A comprehensive A–Z reference of pathology, histopathology, and laboratory medicine terminology. Peer-reviewed definitions for pathologists, residents, researchers and laboratory professionals.
A malignant epithelial neoplasm arising from glandular structures. Adenocarcinomas are among the most common carcinomas and occur in the lung, colon, breast, prostate and many other organs.
HistopathologyA computational procedure or set of rules designed to process pathology data, often used in artificial intelligence systems for automated image analysis, pattern recognition and diagnostic decision support.
Digital PathologyResembling an amoeba in form or movement. In pathology, describes cells that exhibit irregular, flowing cytoplasmic projections, often seen in certain leukaemias and macrophage-lineage cells.
HistopathologyLoss of cellular differentiation and orientation, a hallmark of malignant neoplasms. Anaplastic cells show marked pleomorphism, abnormal mitoses and loss of normal tissue architecture.
HistopathologyThe process of marking or labelling regions of interest on a digital whole slide image, used to create training datasets for machine learning algorithms and for collaborative diagnostic review.
Digital PathologyAn immunoglobulin protein produced by B lymphocytes that specifically binds to an antigen. In diagnostic pathology, antibodies are used extensively in immunohistochemistry and flow cytometry panels.
ImmunologyA molecule capable of inducing an immune response and binding specifically to an antibody or T-cell receptor. Antigen detection forms the basis of immunohistochemical and serological diagnostic assays.
ImmunologyProgrammed cell death characterised by cell shrinkage, chromatin condensation, membrane blebbing and formation of apoptotic bodies. Unlike necrosis, apoptosis does not elicit an inflammatory response.
Cell BiologyA structural or staining abnormality in a histological preparation caused by tissue processing rather than disease. Common artefacts include crush artefact, formalin pigment and tissue folding.
Laboratory MedicineDescribing cells or tissue that deviate from normal morphology but do not meet full criteria for malignancy. Atypical findings often warrant further investigation or close follow-up.
HistopathologyA post-mortem examination performed to determine the cause of death, evaluate disease progression or confirm clinical diagnoses. Autopsies may be clinical (hospital) or forensic (medicolegal).
Anatomical PathologyPertaining to an immune response directed against the body's own tissues. Autoimmune diseases such as lupus, rheumatoid arthritis and autoimmune hepatitis produce characteristic histopathological patterns.
ImmunologyA thin, specialised extracellular matrix underlying epithelial and endothelial cells. Breach of the basement membrane by tumour cells is a key criterion for distinguishing invasive carcinoma from carcinoma in situ.
HistopathologyA fusion oncogene resulting from the t(9;22) Philadelphia chromosome translocation, producing a constitutively active tyrosine kinase. BCR-ABL is the diagnostic hallmark of chronic myeloid leukaemia (CML).
Molecular PathologyA non-cancerous neoplasm that grows locally without invasion or metastasis. Benign tumours are generally well-circumscribed, slow-growing and curable by complete excision.
HistopathologyA measurable biological indicator used to assess disease presence, progression or therapeutic response. Biomarkers may be molecular (e.g. PD-L1), cellular (e.g. Ki-67 index) or biochemical (e.g. PSA).
Molecular PathologyThe removal of a tissue sample from a living patient for histological examination. Types include incisional, excisional, core needle, fine-needle aspiration and punch biopsy.
Anatomical PathologyThe soft tissue within bones responsible for haematopoiesis. Bone marrow biopsy and aspirate examination are essential for diagnosing leukaemias, lymphomas, myelodysplastic syndromes and aplastic anaemia.
HaematopathologyA serine/threonine kinase in the RAS-MAPK signalling pathway. The BRAF V600E mutation is clinically significant in melanoma, colorectal carcinoma, papillary thyroid carcinoma and hairy cell leukaemia.
Molecular PathologyThe thin layer of white blood cells and platelets that forms between the red blood cell layer and plasma after centrifugation of whole blood. Used in laboratory analysis for leucocyte enrichment.
Laboratory MedicineA highly aggressive B-cell non-Hodgkin lymphoma characterised by MYC gene translocation and a starry-sky pattern on histology. Endemic, sporadic and immunodeficiency-associated variants are recognised.
HaematopathologyAn epitope that has been chemically masked during tissue fixation and processing, requiring antigen retrieval techniques (heat-induced or enzymatic) before immunohistochemical staining can be performed.
ImmunohistochemistryA malignant neoplasm arising from epithelial cells. Carcinomas account for the majority of human cancers and are classified by histological subtype (squamous, adenocarcinoma, transitional, etc.).
HistopathologyCluster of differentiation antigens expressed on the surface of leucocytes and other cells. CD markers are essential in immunophenotyping haematological malignancies and classifying lymphoma subtypes.
ImmunologyThe complex of DNA and histone proteins within the cell nucleus. Chromatin patterns (fine, coarse, vesicular, hyperchromatic) are important cytological criteria in distinguishing benign from malignant cells.
Cell BiologyCytokeratin 7, an intermediate filament protein expressed by many glandular and ductal epithelia. CK7 is widely used in immunohistochemistry panels to determine the primary site of metastatic carcinomas.
ImmunohistochemistryCytokeratin 20, an intermediate filament protein with restricted expression in gastrointestinal epithelium, urothelium and Merkel cells. CK20 is used alongside CK7 to identify carcinoma origin.
ImmunohistochemistryA population of cells derived from a single progenitor cell, sharing identical genetic composition. Clonality assessment is fundamental to distinguishing reactive from neoplastic lymphoid proliferations.
Molecular PathologyAn interdisciplinary field combining pathology with computational science, applying algorithms, machine learning and data analytics to digitised tissue images and multi-omic datasets for diagnostic and prognostic purposes.
Digital PathologyA tissue sampling procedure using a hollow-core needle to obtain a cylindrical specimen for histological evaluation. Core biopsies preserve tissue architecture and are commonly used for breast, liver and prostate lesions.
Anatomical PathologyA tissue section prepared by rapid freezing and microtome cutting without paraffin embedding. Cryosections enable intraoperative frozen section diagnosis but yield lower morphological quality than formalin-fixed sections.
Laboratory MedicineThe study of individual cells and cell clusters for diagnostic purposes. Cytological specimens include Pap smears, fine-needle aspirates, body fluid preparations and brushings.
CytopathologyThe material within a cell enclosed by the plasma membrane, excluding the nucleus. Cytoplasmic features such as granularity, vacuolation and eosinophilia provide important diagnostic clues in histopathology.
Cell BiologyThe branch of laboratory medicine concerned with the analysis of body fluids (blood, urine, CSF) for chemical constituents. Clinical chemistry tests include electrolytes, enzymes, hormones and metabolic markers.
Clinical ChemistryA subset of machine learning using multi-layered neural networks to learn complex representations from data. In pathology, deep learning powers automated tumour detection, grading and biomarker quantification from whole slide images.
Digital PathologyThe removal of calcium salts from bone or calcified tissue specimens to enable sectioning on a microtome. Decalcification agents include acids (hydrochloric, formic, nitric) and chelating agents (EDTA).
Laboratory MedicineDigital Imaging and Communications in Medicine, a standard protocol for handling, storing and transmitting medical imaging data. DICOM is increasingly adopted in digital pathology for whole slide image interoperability.
Digital PathologyThe degree to which neoplastic cells resemble their tissue of origin in morphology and function. Well-differentiated tumours retain close resemblance to normal tissue, while poorly differentiated tumours show marked deviation.
HistopathologyThe practice of converting glass slides into high-resolution digital images for viewing, analysis, storage and sharing. Digital pathology enables remote diagnosis, AI-assisted analysis and integrated multi-modal diagnostics.
Digital PathologyAn epigenetic modification involving the addition of a methyl group to cytosine residues, typically at CpG dinucleotides. Aberrant methylation patterns are used as biomarkers in molecular pathology for tumour classification.
Molecular PathologyPertaining to or arising from duct structures. Ductal carcinoma is the most common type of breast cancer, and ductal differentiation is observed in tumours of the pancreas, salivary glands and other organs.
HistopathologyDisordered cell growth and maturation characterised by architectural disorganisation, nuclear atypia and abnormal differentiation. Dysplasia is a pre-malignant condition graded as low-grade or high-grade.
HistopathologyThe growth of fibrous or connective tissue around a tumour, creating a dense stromal reaction. Desmoplastic stroma is characteristic of pancreatic ductal adenocarcinoma and certain breast carcinomas.
HistopathologyThe systematic cutting and examination of a surgical specimen or autopsy organ to identify and sample areas of pathological interest. Proper dissection technique is essential for accurate staging and margin assessment.
Anatomical PathologyEpidermal growth factor receptor, a transmembrane tyrosine kinase. EGFR mutations and amplification are tested in non-small cell lung carcinoma and colorectal carcinoma to guide targeted therapy selection.
Molecular PathologyThe process of infiltrating fixed tissue with a supporting medium (typically paraffin wax) to enable thin sectioning on a microtome. Proper embedding orientation is critical for obtaining diagnostically useful sections.
Laboratory MedicineA granulocytic white blood cell with bilobed nucleus and bright eosinophilic cytoplasmic granules. Tissue eosinophilia is associated with allergic reactions, parasitic infections and certain lymphomas.
HaematopathologyA tissue composed of closely packed cells that lines body surfaces, cavities and glands. Epithelial tissues are classified as squamous, cuboidal, columnar, transitional or pseudostratified.
HistopathologyThe surgical removal of a lesion or organ in its entirety. Excisional specimens require careful margin assessment and orientation to determine completeness of resection.
Anatomical PathologyA targeted next-generation sequencing approach that captures and sequences the protein-coding regions (exons) of the genome. Whole-exome sequencing is used in tumour profiling and rare disease diagnostics.
Molecular PathologyThe non-cellular component of tissues comprising structural proteins, glycoproteins and proteoglycans. ECM composition and remodelling are important in tumour microenvironment assessment and fibrosis grading.
HistopathologyA molecular cytogenetic technique using fluorescent-labelled DNA probes to detect specific chromosomal abnormalities. FISH is used to identify gene amplifications (e.g. HER2), translocations (e.g. BCR-ABL) and deletions.
Molecular PathologyThe chemical or physical preservation of tissue to prevent autolysis and putrefaction. Formalin (10% neutral buffered formaldehyde) is the most widely used fixative in surgical pathology.
Laboratory MedicineA laser-based technique for analysing physical and chemical characteristics of cells in a fluid stream. Flow cytometry is essential for immunophenotyping leukaemias, lymphomas and monitoring minimal residual disease.
Laboratory MedicineA large-scale machine learning model pre-trained on vast datasets that can be fine-tuned for specific downstream tasks. In pathology, foundation models are trained on millions of whole slide images for diverse diagnostic applications.
Digital PathologyA rapid histological technique in which fresh tissue is frozen, sectioned and stained for intraoperative consultation. Frozen sections guide surgical decision-making regarding margins and diagnosis within minutes.
Anatomical PathologyThe excessive deposition of fibrous connective tissue in an organ, often as a reparative or reactive process. Fibrosis staging is critical in liver pathology (e.g. METAVIR score) and interstitial lung disease assessment.
HistopathologyA minimally invasive procedure using a thin needle to aspirate cells from a mass for cytological examination. FNA is commonly used for thyroid nodules, lymph nodes and salivary gland lesions.
CytopathologyA grading system for prostate adenocarcinoma based on architectural patterns of tumour glands. The Gleason score is the sum of the two most prevalent patterns (each graded 1-5) and is a key prognostic indicator.
HistopathologyThe histological assessment of tumour differentiation, cellularity and mitotic activity to stratify biological aggressiveness. Grading systems are tumour-specific and complement staging in determining prognosis.
HistopathologyA focal collection of epithelioid macrophages, often with giant cells, formed as a chronic inflammatory response. Granulomas are seen in tuberculosis, sarcoidosis, fungal infections and foreign body reactions.
HistopathologyThe macroscopic inspection, measurement and description of a surgical specimen or autopsy organ prior to tissue sampling. Accurate gross examination is essential for proper staging, margin assessment and section selection.
Anatomical PathologyA Romanowsky-type stain used for blood smears, bone marrow aspirates and cytological preparations. Giemsa staining differentiates nuclear and cytoplasmic components and is essential for haematological diagnosis.
Laboratory MedicineThe measurement of mRNA levels across thousands of genes simultaneously, typically by microarray or RNA sequencing. Gene expression profiles are used for tumour classification, prognosis and treatment selection.
Molecular PathologyThe most widely used histological stain in diagnostic pathology. Haematoxylin stains nuclei blue-purple, while eosin stains cytoplasm and extracellular matrix pink, providing essential morphological contrast.
Laboratory MedicineA transmembrane receptor tyrosine kinase encoded by the ERBB2 gene. HER2 overexpression or amplification is tested in breast and gastric carcinomas to determine eligibility for anti-HER2 targeted therapy.
Molecular PathologyThe branch of pathology involving the microscopic examination of tissue sections to study disease manifestations. Histopathology is the gold standard for cancer diagnosis, grading and classification.
HistopathologyThe process of complementary nucleic acid strands binding to each other. In molecular pathology, hybridisation techniques (FISH, CISH, ISH) detect specific DNA or RNA sequences within tissue sections or cell preparations.
Molecular PathologyAn increase in the number of cells in a tissue or organ, resulting in enlargement. Hyperplasia may be physiological (e.g. lactating breast) or pathological (e.g. endometrial hyperplasia) and is distinct from neoplasia.
HistopathologyAn increase in cell size without cell division, leading to organ enlargement. Cardiac hypertrophy and skeletal muscle hypertrophy are common examples encountered in pathological and physiological contexts.
HistopathologyA lymphoid neoplasm characterised by the presence of Reed-Sternberg cells within a reactive inflammatory background. Hodgkin lymphoma has distinct subtypes with different histological patterns and prognoses.
HaematopathologyAn iron-storage complex formed from the breakdown of haemoglobin. Haemosiderin deposits appear as golden-brown granules in tissue sections and are highlighted by Prussian blue (Perls) staining.
HistopathologyA colour-coded visual representation of data density or model prediction confidence overlaid on a whole slide image. AI-generated heatmaps highlight regions of diagnostic interest for pathologist review.
Digital PathologyThe process of blood cell formation occurring primarily in the bone marrow. Assessment of haematopoietic lineage maturation is fundamental to the diagnosis of myeloid and lymphoid neoplasms.
HaematopathologyA technique using antibodies to detect specific antigens in tissue sections, visualised by chromogenic or fluorescent reporters. IHC is indispensable for tumour classification, prognostication and predictive biomarker assessment.
ImmunohistochemistryA molecular technique using labelled nucleic acid probes to detect specific DNA or RNA sequences within intact cells or tissue sections. Variants include FISH (fluorescent), CISH (chromogenic) and RNA-ISH.
Molecular PathologyAn area of ischaemic necrosis caused by occlusion of the arterial supply or venous drainage. Infarcts may be white (anaemic) in solid organs or red (haemorrhagic) in organs with dual blood supply.
HistopathologyA complex biological response to tissue injury, infection or irritation involving vascular changes, leucocyte recruitment and mediator release. Inflammation is classified as acute (neutrophilic) or chronic (lymphocytic/macrophagic).
HistopathologyDescribing a neoplasm that has breached the basement membrane and infiltrated surrounding stroma. The distinction between in situ and invasive disease is critical for staging, prognosis and treatment planning.
HistopathologyA mutation in isocitrate dehydrogenase (IDH1 or IDH2) resulting in neomorphic enzyme activity. IDH mutations are diagnostically and prognostically significant in gliomas and acute myeloid leukaemia.
Molecular PathologyThe characterisation of cells based on the antigens they express, performed by flow cytometry or immunohistochemistry. Immunophenotyping is essential for classifying haematological malignancies according to WHO criteria.
ImmunologyThe period of the cell cycle between mitotic divisions, during which DNA replication and cell growth occur. Interphase FISH allows detection of genetic abnormalities in non-dividing cells within tissue sections.
Cell BiologyThe quantitative extraction of measurements from digital pathology images, including cell counts, staining intensity, nuclear morphometry and spatial relationships. Automated image analysis improves objectivity and reproducibility.
Digital PathologyAn abnormal intracellular or intranuclear structure visible on light microscopy. Inclusion bodies may represent viral particles (e.g. CMV owl-eye inclusions), storage products or degenerative changes.
HistopathologyA gain-of-function mutation in the Janus kinase 2 gene, most commonly JAK2 V617F. This mutation is a diagnostic criterion for myeloproliferative neoplasms including polycythaemia vera and essential thrombocythaemia.
Molecular PathologyLocated at or pertaining to the junction between tissue layers, particularly the dermal-epidermal junction. Junctional melanocytic proliferations and junctional nests are key features in melanocytic lesion assessment.
DermatopathologyIn pathology, a descriptor for lesions or conditions occurring in children and adolescents. Examples include juvenile granulosa cell tumour, juvenile polyp and juvenile xanthogranuloma, each with distinct histological features.
HistopathologyThe complete set of chromosomes in a cell, arranged and displayed by size and banding pattern. Karyotyping detects numerical and structural chromosomal abnormalities in haematological malignancies and congenital disorders.
Molecular PathologyA family of intermediate filament proteins expressed by epithelial cells. Keratin expression patterns (cytokeratin profiling) are used in immunohistochemistry to identify cell lineage and determine the primary site of carcinomas.
ImmunohistochemistryA nuclear protein expressed in all active phases of the cell cycle but absent in resting (G0) cells. The Ki-67 proliferation index, assessed by immunohistochemistry, is a key prognostic marker in breast cancer, lymphoma and neuroendocrine tumours.
ImmunohistochemistryAn epithelial cell exhibiting a perinuclear halo and nuclear irregularity, considered the cytopathic hallmark of human papillomavirus (HPV) infection. Koilocytosis is a diagnostic feature of HPV-related squamous lesions.
CytopathologyA proto-oncogene encoding a GTPase in the RAS/MAPK signalling pathway. KRAS mutations are common in pancreatic, colorectal and non-small cell lung carcinomas and predict resistance to anti-EGFR therapy.
Molecular PathologyAny abnormality in tissue structure or function caused by disease or injury. In pathology, the term encompasses a broad spectrum from benign reactive changes to malignant neoplasms.
HistopathologyA group of haematological malignancies characterised by the clonal proliferation of abnormal leucocytes in the bone marrow and blood. Leukaemias are classified as acute or chronic and myeloid or lymphoid.
HaematopathologyA minimally invasive blood test that detects circulating tumour DNA (ctDNA), circulating tumour cells or exosomes shed by tumours. Liquid biopsy enables molecular profiling, treatment monitoring and early detection.
Molecular PathologyA small, encapsulated organ of the lymphatic system that filters lymph and houses immune cells. Lymph node examination is essential for cancer staging and diagnosing lymphoproliferative disorders.
Anatomical PathologyA malignant neoplasm of lymphoid cells arising primarily in lymph nodes and lymphoid tissues. Lymphomas are classified as Hodgkin or non-Hodgkin, with numerous subtypes defined by the WHO classification.
HaematopathologyPertaining to lobules, small structural units within an organ. Invasive lobular carcinoma of the breast is characterised by discohesive cells infiltrating in single-file patterns, often with E-cadherin loss.
HistopathologyThe disintegration or destruction of a cell by disruption of its membrane. Cell lysis may occur through complement activation, osmotic stress, enzymatic digestion or cytotoxic lymphocyte-mediated mechanisms.
Cell BiologyA branch of artificial intelligence in which algorithms learn patterns from data without explicit programming. In pathology, machine learning models are trained to classify tissue types, detect tumours and predict outcomes from histological images.
Digital PathologyDescribing a neoplasm with the capacity for local invasion and distant metastasis. Malignant tumours are characterised by uncontrolled growth, anaplasia, invasion through basement membranes and potential for spread.
HistopathologyThe edge of a surgically resected specimen, assessed microscopically to determine whether tumour extends to the cut surface. Positive (involved) margins often necessitate re-excision or additional treatment.
Anatomical PathologyThe spread of malignant cells from the primary tumour site to distant organs via lymphatic or haematogenous routes. Metastatic disease is a hallmark of malignancy and a major determinant of cancer stage and prognosis.
HistopathologyA laboratory technology using a grid of microscopic spots, each containing DNA, RNA or protein probes. Tissue microarrays (TMAs) enable high-throughput immunohistochemical and molecular analysis of hundreds of specimens simultaneously.
Molecular PathologyA precision cutting instrument used to produce thin tissue sections (typically 3-5 micrometres) from paraffin-embedded blocks for mounting on glass slides and staining.
Laboratory MedicineThe process of cell division resulting in two genetically identical daughter cells. The mitotic count (number of mitoses per unit area) is a key parameter in tumour grading systems for sarcomas, melanoma and other neoplasms.
Cell BiologyThe subspecialty of pathology focused on the study of disease at the molecular level using DNA, RNA and protein-based techniques. Molecular pathology underpins precision medicine through biomarker testing and genomic profiling.
Molecular PathologyThe study of the form, structure and configuration of cells and tissues. Morphological assessment remains the foundation of histopathological diagnosis, encompassing nuclear, cytoplasmic and architectural features.
HistopathologyPertaining to or characterised by abundant mucin production. Mucinous carcinomas are recognised subtypes in the breast, ovary, colon, pancreas and lung, each with distinct biological behaviour.
HistopathologyAn advanced technique enabling simultaneous detection of multiple protein markers on a single tissue section using spectrally distinct fluorophores. Multiplex IF is used to characterise the tumour immune microenvironment.
ImmunohistochemistryA condition of genetic hypermutability resulting from deficient DNA mismatch repair. MSI-high tumours, most commonly colorectal and endometrial carcinomas, are associated with response to immune checkpoint inhibitor therapy.
Molecular PathologyPremature, uncontrolled cell death characterised by cell swelling, membrane disruption and inflammatory response. Types include coagulative, liquefactive, caseous, fat and fibrinoid necrosis, each with distinct morphological patterns.
HistopathologyAn abnormal mass of tissue resulting from autonomous, uncontrolled cell proliferation. Neoplasms may be benign (localised, non-invasive) or malignant (invasive, capable of metastasis).
HistopathologyThe most abundant granulocytic leucocyte, characterised by a multilobed nucleus and fine cytoplasmic granules. Neutrophils are the primary effector cells of acute inflammation and form the basis of purulent exudates.
HaematopathologyHigh-throughput DNA or RNA sequencing technologies that enable simultaneous analysis of multiple genes or entire genomes. NGS panels are used in oncology for comprehensive tumour genomic profiling and therapy selection.
Molecular PathologyA histological assessment of nuclear size, shape, chromatin pattern and nucleolar prominence. Nuclear grading is a component of several tumour grading systems, including Fuhrman grading for renal cell carcinoma.
HistopathologyThe proportion of cell area occupied by the nucleus relative to the cytoplasm. An increased N:C ratio is a cytological feature of malignancy and is assessed in both histological and cytological preparations.
CytopathologyA histological grading system for invasive breast carcinoma based on tubule formation, nuclear pleomorphism and mitotic count. The Nottingham grade (modified Bloom-Richardson) is a key prognostic factor in breast cancer.
HistopathologyA mutated or overexpressed gene that drives uncontrolled cell proliferation and contributes to tumour development. Oncogenes include growth factor receptors (HER2, EGFR), signalling molecules (KRAS, BRAF) and transcription factors (MYC).
Molecular PathologyA three-dimensional in vitro tissue model derived from stem cells or primary tissue that recapitulates the architecture and function of the organ of origin. Organoids are used in drug testing, disease modelling and personalised medicine.
Molecular PathologyA primary malignant bone tumour characterised by the production of osteoid matrix by neoplastic cells. Osteosarcoma is the most common primary bone cancer, predominantly affecting adolescents and young adults.
HistopathologyA quantitative measure of light absorbance through a stained tissue section or specimen. Optical density measurements are used in digital pathology for standardising staining intensity and quantitative immunohistochemistry.
Digital PathologyA tumour suppressor protein encoded by the TP53 gene, often called the "guardian of the genome." Aberrant p53 expression detected by immunohistochemistry (overexpression or complete absence) indicates TP53 mutation in many cancer types.
Molecular PathologyDescribing a growth pattern characterised by finger-like projections with fibrovascular cores covered by epithelium. Papillary architecture is seen in papillary thyroid carcinoma, papillary renal cell carcinoma and papillary urothelial neoplasms.
HistopathologyThe biological mechanism by which a disease develops and progresses. Understanding pathogenesis is fundamental to identifying diagnostic markers and therapeutic targets.
HistopathologyA molecular biology technique for amplifying specific DNA sequences exponentially. PCR and its variants (RT-PCR, qPCR, digital PCR) are used for mutation detection, pathogen identification and clonality assessment.
Molecular PathologyAn immune checkpoint protein expressed on tumour cells and immune cells. PD-L1 expression, assessed by immunohistochemistry, is a predictive biomarker for immune checkpoint inhibitor therapy in lung, bladder and other cancers.
ImmunohistochemistryVariation in cell and nuclear size and shape within a tumour. Marked pleomorphism is typically associated with high-grade malignancy and is assessed as part of nuclear grading systems.
HistopathologyThe predicted course and outcome of a disease. Pathological prognostic factors include tumour type, grade, stage, margin status, lymphovascular invasion and molecular biomarker profile.
Clinical PathologyThe process of cell growth and division. Proliferative activity is assessed by mitotic counts, Ki-67 labelling index or phosphohistone H3 staining and is a key determinant of tumour grade and behaviour.
Cell BiologyA medical approach that tailors treatment based on individual patient and tumour molecular characteristics. Pathology provides the biomarker testing (IHC, FISH, NGS) that underpins precision oncology treatment selection.
Molecular PathologyFactors occurring before laboratory analysis that affect specimen quality and test results, including fixation time, ischaemia time, tissue handling and specimen transport conditions.
Laboratory MedicineA grossly visible projection arising from a mucosal surface. Polyps are classified histologically as hyperplastic, inflammatory, hamartomatous or neoplastic (adenomatous), with different malignant potential.
HistopathologySystematic processes implemented in pathology laboratories to ensure accuracy, reliability and consistency of diagnostic results. QA programmes include proficiency testing, internal audits and external quality assessment schemes.
Laboratory MedicineA molecular technique that measures the quantity of a specific DNA or RNA target in real time during amplification. qPCR is used for viral load quantification, gene expression analysis and minimal residual disease monitoring.
Molecular PathologyOperational techniques and activities used to monitor and evaluate laboratory processes, ensuring that predefined quality standards are met. QC includes daily control specimens, calibration checks and staining verification.
Laboratory MedicineA protein on the cell surface or within the cell that binds specific ligands and triggers a biological response. Receptor status (ER, PR, HER2, androgen receptor) is critical in tumour classification and therapy selection.
Molecular PathologyThe surgical removal of part or all of a tissue or organ. Resection specimens are examined by pathologists for tumour type, grade, stage, margin status and lymph node involvement.
Anatomical PathologyRibonucleic acid, a single-stranded nucleic acid involved in gene expression and regulation. RNA analysis (RT-PCR, RNA sequencing, RNA-ISH) is used in molecular pathology for gene expression profiling and fusion gene detection.
Molecular PathologyA large, binucleated or multinucleated cell with prominent eosinophilic nucleoli, considered the hallmark neoplastic cell of classical Hodgkin lymphoma. Reed-Sternberg cells are typically CD30-positive and CD15-positive.
HaematopathologyThe partial or complete disappearance of a tumour, either spontaneously or following treatment. Histological evidence of regression includes fibrosis, melanophages and inflammatory infiltrates replacing viable tumour.
HistopathologyA silver-based histochemical stain that highlights reticular fibres (type III collagen) in tissue sections. Reticulin staining is essential for assessing bone marrow fibrosis and hepatic architecture.
Laboratory MedicineA malignant neoplasm arising from mesenchymal (connective) tissues including bone, cartilage, fat, muscle and vascular tissue. Sarcomas are classified by histological type and graded by differentiation, mitotic count and necrosis.
HistopathologyThe first lymph node to receive lymphatic drainage from a primary tumour. Sentinel lymph node biopsy is a staging procedure used in breast cancer and melanoma to assess regional metastatic spread.
Anatomical PathologyA high-resolution imaging device that digitises glass microscope slides into whole slide images (WSI). Slide scanners are the foundational hardware enabling digital pathology workflows and AI-based image analysis.
Digital PathologyA malignant epithelial neoplasm showing squamous differentiation, characterised by keratinisation and intercellular bridges. Squamous cell carcinomas arise in the skin, lung, oesophagus, cervix, head and neck and other sites.
HistopathologyThe systematic classification of cancer extent using the TNM system: Tumour size/extent (T), regional lymph Node involvement (N) and distant Metastasis (M). TNM staging determines prognosis and guides treatment decisions.
Clinical PathologyThe application of dyes or reagents to tissue sections to enhance visualisation of cellular and extracellular components. Staining techniques include routine (H&E), special (PAS, trichrome, silver) and immunohistochemical methods.
Laboratory MedicineThe supportive connective tissue framework of an organ or tumour. Tumour stroma, including fibroblasts, blood vessels and immune cells, forms the tumour microenvironment and influences tumour behaviour and treatment response.
HistopathologyA technology that maps gene expression data to specific locations within a tissue section, preserving spatial context. Spatial transcriptomics bridges the gap between morphology and molecular biology in tissue analysis.
Molecular PathologyA structured, standardised format for pathology reports using checklists of required data elements. Synoptic reporting improves completeness, consistency and data extraction for cancer registries and clinical trials.
Clinical PathologyA histochemical staining method that selectively highlights specific tissue components or organisms not adequately demonstrated by H&E. Examples include PAS, Masson trichrome, Congo red, Ziehl-Neelsen and Grocott methenamine silver.
Laboratory MedicineThe formation of a blood clot (thrombus) within a vessel, obstructing blood flow. Thrombosis is identified histologically by the presence of fibrin, platelets, trapped red cells and leucocytes within the vascular lumen.
HistopathologyA paraffin block containing cylindrical cores from multiple tissue specimens arranged in a grid. TMAs enable simultaneous high-throughput analysis of hundreds of cases with a single immunohistochemical or molecular assay.
Laboratory MedicineThe total number of somatic mutations per megabase of interrogated genomic sequence in a tumour. High TMB is associated with increased neoantigen production and response to immune checkpoint inhibitor therapy.
Molecular PathologyThe process of prioritising specimens or cases for processing and reporting based on clinical urgency. In digital pathology, AI-assisted triage can route cases to appropriate subspecialist pathologists and prioritise urgent diagnoses.
Digital PathologyAn abnormal mass resulting from excessive cell proliferation. Tumours may be benign (localised) or malignant (invasive and metastatic). The term is sometimes used synonymously with neoplasm in clinical practice.
HistopathologyThe complex ecosystem surrounding a tumour, comprising immune cells, fibroblasts, blood vessels, extracellular matrix and signalling molecules. Assessment of the tumour microenvironment informs immunotherapy response prediction.
ImmunologyThe duration from specimen receipt to report issuance in a pathology laboratory. TAT is a key quality metric, with targets varying by specimen type (e.g. 48 hours for biopsies, 24 hours for frozen sections).
Laboratory MedicineA cell type found in urothelium capable of stretching. Transitional cell (urothelial) carcinoma is the most common malignancy of the bladder, renal pelvis and ureter.
HistopathologyA machine learning technique where a model trained on one dataset is adapted for a different but related task. Transfer learning allows pathology AI models to achieve high accuracy with limited labelled training data.
Digital PathologyA standardised system for reporting thyroid fine-needle aspiration cytology results in six diagnostic categories, each with an implied risk of malignancy and recommended clinical management.
CytopathologyA defect in an epithelial surface extending through the basement membrane into the underlying tissue. In melanoma, ulceration is an adverse prognostic factor incorporated into AJCC staging.
HistopathologyDescribing a neoplasm that lacks morphological features of any specific cell lineage. Undifferentiated carcinomas require extensive immunohistochemical workup and molecular testing for classification and treatment planning.
HistopathologyA malignant neoplasm arising from the urothelium (transitional epithelium) lining the urinary tract. Urothelial carcinoma is the most common type of bladder cancer and is classified as non-invasive (papillary, flat) or invasive.
HistopathologyA specific alteration in a DNA sequence compared to a reference genome. In molecular pathology, variant classification (pathogenic, likely pathogenic, VUS, likely benign, benign) guides clinical interpretation and treatment decisions.
Molecular PathologyThe presence of tumour cells within blood vessels (angioinvasion) or lymphatic channels (lymphovascular invasion). Vascular invasion is an adverse prognostic factor in many carcinomas and is assessed in surgical pathology reports.
HistopathologyHaving a finger-like or frond-like architecture. Villous adenomas of the colon have a higher malignant potential than tubular adenomas, and villous architecture is noted in certain papillary neoplasms.
HistopathologyMorphological changes in cells caused by viral infection, including nuclear enlargement, multinucleation, ground-glass nuclei and inclusion bodies. Recognising viral cytopathic effects is important in surgical and cytopathology.
HistopathologyThe scanning and digitisation of an entire glass microscope slide at high magnification to create a navigable digital image. WSI is the cornerstone of digital pathology, enabling remote diagnosis, AI analysis and archival storage.
Digital PathologyThe World Health Organization Classification of Tumours, the international standard for tumour nomenclature, diagnostic criteria and grading. The WHO Blue Books are essential references for pathologists worldwide.
Clinical PathologyA laboratory technique for detecting specific proteins in a tissue or cell lysate using gel electrophoresis and antibody-based detection. Western blotting is used in research and confirmatory diagnostic testing.
Laboratory MedicineA silver-based histochemical stain used to detect spirochaetes, Helicobacter organisms and other bacteria in tissue sections. The organisms appear as dark structures against a yellow-brown background.
Laboratory MedicineA localised deposit of lipid-laden macrophages (foam cells) in the skin or subcutaneous tissue, associated with hyperlipidaemia. Xanthomas are identified histologically by collections of foamy histiocytes.
DermatopathologyA rare autosomal recessive disorder of nucleotide excision repair, resulting in extreme sensitivity to ultraviolet radiation. Affected individuals develop multiple skin cancers at an early age, studied extensively in dermatopathology.
Molecular PathologyPertaining to genes located on the X chromosome. X-linked conditions relevant to pathology include Fabry disease, haemophilia and Duchenne muscular dystrophy, each with characteristic histological findings.
Molecular PathologyA malignant germ cell neoplasm that recapitulates yolk sac structures, characterised by Schiller-Duval bodies on histology. Yolk sac tumours produce alpha-fetoprotein (AFP) and occur in the gonads and extragonadal sites.
HistopathologyThe proportion of diagnostic or informative results obtained from a test or procedure. In pathology, biopsy yield and cytology adequacy rates are important quality metrics for specimen collection techniques.
Laboratory MedicineAn acid-fast histochemical stain used to identify mycobacteria (including Mycobacterium tuberculosis) in tissue sections and smears. Acid-fast bacilli appear bright red against a blue counterstain.
Laboratory MedicineThe organised arrangement of cells into distinct functional zones within an organ. In hepatic pathology, lobular zonation (zones 1-3) determines the pattern of injury in various liver diseases.
HistopathologySecretory granules containing inactive enzyme precursors (zymogens) found in pancreatic acinar cells and chief cells. Zymogen granule patterns are assessed in pancreatic pathology and acinar cell carcinoma diagnosis.
Histopathology