RANZCR Pathology key terms

The autonomous, excessive growth of cells that persists after the stimulus causing it has stopped, usually due to acquired genetic alterations. Growth is uncoordinated with normal tissue and can be benign or malignant.

Disordered, atypical cellular growth with loss of normal maturation and orientation, confined by the basement membrane. It is a pre-malignant change; severe dysplasia merges with carcinoma in situ.

Reversible replacement of one mature, differentiated cell type by another that is better adapted to a chronic stressor, such as squamous change in bronchial epithelium in smokers. It is not itself malignant but may predispose to cancer.

An increase in the number of cells in a tissue or organ, usually in response to a stimulus and often reversible. It differs from hypertrophy, which is enlargement of existing cells.

Shrinkage of a tissue or organ due to a reduction in cell size or cell number after normal growth has been achieved. Causes include disuse, denervation, ischaemia, malnutrition and ageing.

Programmed, energy-dependent cell death producing cell shrinkage, chromatin condensation and membrane-bound apoptotic bodies that are phagocytosed without inflammation. It removes damaged or unwanted cells.

Uncontrolled cell death in living tissue from injury, causing cell swelling, membrane rupture and leakage of contents that provokes inflammation. Patterns include coagulative, liquefactive, caseous and fat necrosis.

A focal collection of activated macrophages (epithelioid histiocytes), often with multinucleate giant cells and a rim of lymphocytes, formed in response to persistent antigens. Caseating granulomas suggest tuberculosis; non-caseating forms occur in sarcoidosis and Crohn disease.

Excessive deposition of collagen and other extracellular matrix proteins replacing normal tissue after injury or chronic inflammation. It may be reversible or progressive and causes organ dysfunction and architectural distortion.

Formation of a solid blood clot (thrombus) within the lumen of a vessel or heart chamber during life. It is promoted by endothelial injury, abnormal blood flow and hypercoagulability.

The passage of a detached solid, liquid or gaseous mass through the bloodstream, which lodges in a vessel and obstructs flow. Common types include thromboembolism, fat embolism, air embolism and amniotic fluid embolism.

Death of tissue (ischaemic necrosis) due to inadequate arterial supply or venous drainage. The resulting infarct is usually pale in solid organs with end-arterial supply and haemorrhagic in loosely textured or dual-supply organs such as lung.

A chronic arterial disease in which lipid-rich plaques form in the intima of large and medium arteries, causing narrowing, plaque rupture and thrombosis. It underlies ischaemic heart disease, stroke and peripheral vascular disease.

A group of disorders caused by extracellular deposition of misfolded fibrillar proteins with a beta-pleated sheet structure. Deposits stain with Congo red and show apple-green birefringence under polarised light, causing organ dysfunction.

A malignant epithelial proliferation confined to the epithelium by an intact basement membrane, without invasion of underlying stroma. It has not metastasised but may progress to invasive carcinoma.

The spread of malignant cells from a primary tumour to a distant site via lymphatics, blood vessels, body cavities or direct seeding, where they form secondary tumours. It is the principal cause of cancer death.

A pathological assessment of how closely tumour cells resemble their normal counterparts, based on differentiation, mitotic activity and pleomorphism. Higher grade generally indicates more aggressive behaviour and poorer prognosis.

The classification of the anatomical extent of a cancer, including primary tumour size, nodal involvement and distant spread, usually by the TNM system. Stage correlates more strongly with prognosis than grade and guides treatment.

A diffuse hepatic process of bridging fibrosis and regenerative nodules that distorts liver architecture and vasculature. Consequences include portal hypertension, hepatocellular carcinoma and hepatic failure.

Abnormal accumulation of triglyceride droplets within hepatocytes, producing a macrovesicular or microvesicular fatty change. Causes include alcohol, obesity, metabolic syndrome, drugs and toxins.

A renal syndrome defined by heavy proteinuria, hypoalbuminaemia, generalised oedema and hyperlipidaemia. It results from glomerular disease that increases permeability to protein.

A renal syndrome characterised by haematuria with red cell casts, hypertension, oliguria and mild proteinuria, reflecting glomerular inflammation. It is typical of acute post-infectious glomerulonephritis and other proliferative glomerular diseases.

Inflammation of the renal glomeruli, usually immune-mediated, producing haematuria, proteinuria and declining renal function. It may be proliferative, crescentic or membranous and can progress to chronic kidney disease.

Ischaemic necrosis of heart muscle, most often from acute coronary artery thrombosis on a ruptured atherosclerotic plaque. It causes chest pain, ECG changes and release of troponin, and may be transmural or subendocardial.

Acute inflammation of lung parenchyma, usually infective, with alveolar exudate causing consolidation. Patterns include lobar, bronchopneumonia and interstitial pneumonia.

A localised collection of pus within a newly formed cavity, walled off by inflammation and granulation tissue. It contains neutrophils, necrotic debris and often bacteria, and may require drainage.

Infection of bone and marrow, often by Staphylococcus aureus, causing inflammation, bone necrosis (sequestrum) and reactive new bone (involucrum). It may be acute or chronic and is diagnosed with imaging, culture and histology.

An autoimmune chronic lymphocytic thyroiditis with germinal centres, Hurthle cell change and fibrosis, causing gradual hypothyroidism. It is the commonest cause of hypothyroidism in iodine-sufficient regions.

A germ cell tumour containing tissues derived from more than one embryonic germ layer, sometimes with mature elements such as hair, teeth or bone. Mature cystic teratomas are usually benign; immature teratomas are malignant.

A malignant neoplasm arising from lymphocytes, usually presenting as solid masses in lymph nodes or extranodal tissue. It is divided broadly into Hodgkin and non-Hodgkin types, distinguished by histology and immunophenotype.

A technique using antibodies labelled with a detectable marker to identify specific antigens in tissue sections. In pathology it is used to classify tumours, determine cell lineage and detect infectious organisms.

Rapid intraoperative histological examination of fresh tissue that has been frozen, sectioned and stained. It is used to confirm diagnosis, assess surgical margins and identify lymph node metastases during surgery.

Microscopic examination of individual cells or small clusters obtained by exfoliation or aspiration, such as fine-needle aspiration. It is used to screen for cervical cancer and to sample masses, but lacks architectural information.

Post-mortem examination of a body to determine the cause of death, extent of disease and effects of treatment. It may be hospital-based or medico-legal (coronial) and includes external, internal and histological assessment.

Inadequate blood supply to a tissue or organ, reducing oxygen and nutrients and impairing removal of metabolites. Persistent ischaemia causes cell injury and, if severe, infarction.

Abnormal accumulation of fluid in interstitial tissue spaces or body cavities. Causes include increased hydrostatic pressure, reduced oncotic pressure, lymphatic obstruction and increased vascular permeability.

Increased blood flow to a tissue due to active arteriolar dilatation, producing redness and warmth, as in inflammation or exercise. It differs from congestion, which is passive venous engorgement.