PA H8 | Lymphadenopathy & Lymphomas — Glossary

A microorganism (classically Mycobacterium tuberculosis) whose cell wall lipid (mycolic acid) content allows it to retain the carbol fuchsin stain after acid-alcohol decolourisation in the Ziehl-Neelsen technique.

A four-stage classification (I–IV) for lymphoma based on the number of lymph node regions involved and whether disease crosses the diaphragm or involves extralymphatic organs; modified by A/B suffix for absence/presence of constitutional symptoms.

Constitutional symptoms in the context of lymphoma staging: unexplained fever > 38°C, drenching night sweats, and > 10% body weight loss over 6 months. Their presence designates 'B' suffix in Ann Arbor staging (e.g., Stage IIIB).

An anti-apoptotic protein encoded by the BCL2 gene at chromosome 18; overexpressed in follicular lymphoma due to the t(14;18) translocation, which juxtaposes BCL2 to the immunoglobulin heavy-chain enhancer. Its expression in a follicular lesion is a key differentiating feature from benign follicular hyperplasia.

An anti-apoptotic protein encoded on chromosome 18; constitutively overexpressed in follicular lymphoma due to t(14;18) translocation, preventing programmed cell death of malignant germinal-centre B cells.

The optical property of collagen fibres to rotate polarised light, appearing bright white under polarised microscopy; used to confirm the broad collagen bands of nodular sclerosis HL.

A highly aggressive B-cell NHL with the fastest doubling time of any human tumour (~24 h), characterised by t(8;14)/MYC translocation, near-100% Ki-67, starry-sky pattern on H&E, and strong EBV association in the endemic African form.

A distinct form of coagulative-like necrosis unique to TB (and a few other granulomatous diseases), producing structureless, eosinophilic, crumbly material resembling cheese; no cell outlines are preserved.

A carbohydrate surface antigen expressed on Reed-Sternberg cells in classical Hodgkin lymphoma; its co-expression with CD30 helps distinguish HL from other large-cell lymphomas.

A TNF receptor superfamily member expressed on Reed-Sternberg cells in Hodgkin lymphoma and on anaplastic large cell lymphoma cells; the target of the antibody-drug conjugate brentuximab vedotin.

An activation antigen of the TNF receptor superfamily; strongly expressed on RS cell membranes and Golgi zone in cHL; also positive in ALCL and embryonal carcinoma.

Common leukocyte antigen expressed on the surface of virtually all haemopoietic cells; its absence in RS cells is a key distinguishing IHC feature from reactive lymphocytes and most other lymphomas.

A fluctuant collection of liquefied caseous material (and later true pus) in TB, so-called because the overlying skin is NOT red or hot — owing to the absence of pyogenic bacteria and prostaglandin-driven hyperaemia.

A tuberculous abscess that erodes through the deep cervical fascia, creating a bilocular collection (deep and superficial components connected by a narrow channel) — the 'collar stud' shape on clinical examination.

Outermost compartment of the lymph node, containing B-cell follicles (primary and secondary); site of follicular hyperplasia in B-cell-stimulated states.

Paracortical hyperplasia with melanin-laden macrophages and Langerhans cells in lymph nodes draining regions of chronic inflammatory skin disease (eczema, psoriasis, exfoliative dermatitis).

The commonest NHL subtype overall (~30–35%), consisting of large B cells growing diffusely without follicular architecture; CD20+; aggressive but potentially curable with R-CHOP in ~60% of patients.

Detectable by EBER in-situ hybridisation in RS cells in 30–50% of cHL (mainly MC and LD subtypes); the virus likely contributes to RS cell survival by constitutively activating NF-κB.

Reactive eosinophil infiltration driven by IL-5 secreted by RS cells; particularly prominent in mixed cellularity HL and eosinophilia on peripheral blood smear is an associated paraneoplastic finding.

A macrophage activated by IFN-γ that acquires abundant pale cytoplasm and an elongated kidney-shaped nucleus, resembling epithelial cells histologically; the principal cell of granulomatous inflammation.

Lymph node located above the medial epicondyle of the elbow; normally impalpable; when enlarged, suggests sarcoidosis, syphilis (secondary), cat-scratch disease, or lymphoma.

A herpesvirus (HHV-4) that infects B cells via CD21; associated with Burkitt lymphoma (endemic), Hodgkin lymphoma (mixed cellularity), post-transplant lymphoproliferative disorder, and NK/T-cell lymphoma.

Surgical removal of an intact lymph node for histopathological examination; the preferred investigation when lymphoma is suspected, as it preserves nodal architecture essential for WHO subclassification.

The gross cut-surface descriptor for lymph node replacement in HL and many lymphoid tumours: homogeneous, pale grey-white, and smooth, resembling the cut surface of raw fish.

Fine-Needle Aspiration Cytology — a minimally invasive procedure using a fine-gauge needle to aspirate cells from a node for cytological (not histological) examination; adequate for TB and metastatic carcinoma, insufficient for lymphoma subclassification.

A minimally invasive technique using a fine needle to aspirate cells from a node or mass for cytological examination; first-line investigation for TB lymphadenitis, yielding epithelioid clusters and giant cells.

Reactive enlargement of B-cell follicles with prominent germinal centres containing tingible-body macrophages; caused by B-cell stimulation in RA, SLE, early HIV, and bacterial infections.

The commonest indolent B-cell NHL, arising from germinal-centre cells; characterised by back-to-back neoplastic follicles, t(14;18) translocation causing BCL2 overexpression, and BCL2 positivity within follicles.

A multinucleate cell formed by macrophage fusion in response to inert foreign material; nuclei are centrally and randomly distributed — contrasting with the peripheral horseshoe arrangement in Langhans giant cells.

A cartridge-based nucleic acid amplification test that detects M. tuberculosis DNA and rifampicin-resistance mutations within 2 hours from clinical specimens; WHO-recommended first-line rapid diagnostic tool.

The pale-staining zone within a secondary lymphoid follicle where antigen-activated B cells undergo clonal expansion, somatic hypermutation (affinity maturation), and class-switch recombination.

A compact, organised aggregate of activated macrophages (epithelioid histiocytes), often with giant cells and a lymphocytic cuff, formed in response to a persistent, non-degradable antigen or pathogen.

A cytokine secreted by activated Th1 CD4+ T cells and NK cells that is the master macrophage-activating signal, driving conversion of resting macrophages into epithelioid histiocytes in TB.

A technique using antibodies conjugated to detectable markers to identify specific proteins in tissue sections; essential for lymphoma subtyping, distinguishing HL from NHL, and determining cell of origin in NHL.

A nuclear protein expressed in all phases of the cell cycle except G0; its immunohistochemical labelling index estimates the proliferative fraction of a tumour — ~100% in Burkitt lymphoma, <20% in follicular lymphoma.

A variant of the Reed-Sternberg cell seen in nodular sclerosis Hodgkin lymphoma; the cell retracts in formalin-fixed tissue, creating an empty space (lacuna) around the nucleus.

A multinucleate cell formed by fusion of epithelioid histiocytes, characterised by nuclei arranged in a peripheral horseshoe or wreath pattern; the hallmark cell of tuberculous (and similar) granulomas.

The neoplastic cell of nodular lymphocyte-predominant Hodgkin lymphoma; large, multilobated B cell expressing CD20 and CD45 but not CD15 or CD30, resembling exploded popcorn on H&E.

Enlargement of a lymph node beyond normal size (> 1 cm in adults in most regions); may be reactive, neoplastic, or granulomatous in origin.

A malignant neoplasm of lymphoid cells that proliferates as a solid tumour mass, typically in lymph nodes or extranodal lymphoid tissues, distinguishing it from leukaemia where the neoplastic clone predominates in blood and marrow.

Lymph nodes adherent to each other and surrounding tissue due to periadenitis and extracapsular fibrosis; a gross feature seen in HL and other inflammatory/malignant lymphadenopathies.

Macrophage-lined channels in the central medulla of the lymph node through which lymph percolates before exiting via the efferent lymphatic; site of sinus histiocytosis.

The second most common cHL subtype, characterised by classic RS cells in a polymorphous background of eosinophils, plasma cells, histiocytes, and lymphocytes without collagen bands; strongly EBV-associated.

A classical Hodgkin lymphoma subtype with classic RS cells against a rich mixed inflammatory background, strongly associated with EBV (~70%); more common in older males and in advanced disease.

A mononuclear RS variant with a single nucleus bearing a prominent eosinophilic nucleolus; present in all cHL subtypes but non-diagnostic alone.

A degenerate RS cell with pyknotic, shrunken nucleus and deeply eosinophilic homogeneous cytoplasm; seen in lymphocyte-depleted HL and post-treatment necrotic areas.

A transcription factor proto-oncogene that drives cell proliferation and ribosome biogenesis; constitutively overexpressed in Burkitt lymphoma due to t(8;14), resulting in uncontrolled rapid cell division.

A biologically distinct HL variant with popcorn cells (L&H cells) in a nodular B-cell background; CD20+/CD30−/CD15−; indolent course, treated differently from cHL.

The most common Hodgkin lymphoma subtype (60–80%), defined by broad birefringent collagen bands dividing the node into cellular nodules containing lacunar cells.

The commonest classical Hodgkin lymphoma subtype, characterised by collagen bands dividing the lymph node into nodules and lacunar-cell RS variants; predominantly affects young women with mediastinal disease.

A tight, well-formed epithelioid granuloma lacking central caseous necrosis; the hallmark of sarcoidosis; its absence distinguishes sarcoidosis from TB histologically.

The distinctive large, round, centrally placed eosinophilic nucleolus with a surrounding clear halo seen in the RS cell; one per nuclear lobe, giving the characteristic 'owl' appearance in the binucleate cell.

Thymus-dependent (T-cell) zone of the lymph node, deep to the cortex; expands in viral infections, drug reactions, and after vaccination.

Expansion of the T-cell zone (paracortex) with immunoblasts; the dominant pattern in viral lymphadenopathy (EBV, CMV) and drug reactions.

B-cell transcription factor retained in RS cells at dim intensity, confirming germinal-centre B-cell origin despite loss of most other B-cell markers (CD20, CD79a).

Inflammation extending beyond the lymph node capsule into the surrounding perinodal fat, causing node matting (fusion of adjacent nodes into a conglomerate mass); characteristic of tuberculous lymphadenitis.

Enlargement of lymph nodes in two or more extra-inguinal sites, lasting > 3 months, without another explanation; a WHO clinical stage 1 feature of HIV infection caused by follicular hyperplasia driven by polyclonal B-cell stimulation.

The inflammatory infiltrate comprising 95–99% of the HL tumour mass, driven by cytokines from RS cells; includes lymphocytes, eosinophils, plasma cells, histiocytes, and variable fibrosis.

The neoplastic cell of nodular lymphocyte-predominant Hodgkin lymphoma; large with a lobulated 'popcorn'-shaped nucleus, multiple small nucleoli, and CD20+/CD30−/CD15− immunophenotype.

Non-neoplastic enlargement of a lymph node due to immunological stimulation; subtypes are follicular, paracortical, and sinus histiocytosis based on the predominant compartment affected.

The pathognomonic large binucleate or multinucleate B-cell-derived malignant cell of classical Hodgkin lymphoma, characterised by prominent eosinophilic owl-eye nucleoli and the immunophenotype CD15+/CD30+/CD45−.

The large, binucleate neoplastic cell pathognomonic of classic Hodgkin lymphoma, characterised by mirror-image nuclei each containing a large eosinophilic 'owl-eye' nucleolus with a surrounding clear halo.

The transformation of chronic lymphocytic leukaemia or small lymphocytic lymphoma to a more aggressive lymphoma, usually DLBCL, associated with rapid clinical deterioration and poor prognosis.

A non-tender, firm-elastic feel to a lymph node on palpation, classically described in Hodgkin lymphoma; distinct from the stony hardness of metastatic carcinoma and the soft fluctuance of an acute abscess.

A multisystem granulomatous disease of unknown aetiology characterised by non-caseating epithelioid granulomas; lymph node involvement is common (bilateral hilar, cervical, supraclavicular).

Laminated, calcium-phosphate-containing inclusions found inside giant cells in sarcoid granulomas (and occasionally TB); their presence in a non-caseating granuloma supports sarcoidosis.

Cervical tuberculous lymphadenitis; the commonest form of extrapulmonary TB, presenting as matted painless cervical lymphadenopathy with caseous necrosis.

Distension of medullary and subcapsular sinuses by proliferating macrophages; occurs in lymph nodes draining carcinoma and in Rosai-Dorfman disease.

A chronic discharging tract lined with granulation tissue, formed when a cold abscess spontaneously ruptures through the skin surface, resulting in persistent discharge of caseous/seropurulent material.

A histological appearance in Burkitt lymphoma created by pale tingible-body macrophages (the 'stars') engulfing apoptotic debris scattered against a dark background of densely packed, rapidly proliferating lymphoma cells (the 'sky').

A grade 2 nodular sclerosis pattern where lacunar cells form cohesive sheets ('syncytia'), with depleted lymphocytic background and higher-grade clinical behaviour.

The chromosomal translocation juxtaposing BCL2 (chromosome 18q21) with the IgH locus (chromosome 14q32), placing BCL2 under the constitutive immunoglobulin promoter; pathognomonic of follicular lymphoma.

The chromosomal translocation placing the MYC proto-oncogene (chromosome 8q24) under the IgH promoter (chromosome 14q32), causing constitutive MYC-driven proliferation; the hallmark of Burkitt lymphoma.

Tuberculous lymphadenitis of mesenteric lymph nodes, historically a cause of abdominal pain and intestinal obstruction in children; the mesenteric equivalent of scrofula.

A macrophage in a germinal centre that contains engulfed, apoptotic lymphocyte debris ('tingible bodies'); their presence signifies active B-cell turnover and distinguishes reactive follicular hyperplasia from follicular lymphoma.

Palpable enlargement of the left supraclavicular (Virchow's) lymph node, indicating metastatic carcinoma from a sub-diaphragmatic (usually gastric) primary.

A single, discrete, organised epithelioid granuloma with a central zone of caseous necrosis, the fundamental histopathological unit of TB; multiple tubercles coalesce to form confluent lesions in lymph nodes.

Cell-mediated delayed hypersensitivity reaction driven by CD4+ Th1 lymphocytes and activated macrophages, with no antibody involvement; peaks 48–72 h after antigen exposure; the immunological basis of granuloma formation.

The left supraclavicular lymph node (sentinel node of Troisier); its enlargement indicates metastatic spread from abdominal, pelvic, or thoracic primary tumours via the thoracic duct.

A differential stain using hot carbol fuchsin + acid-alcohol decolourisation + methylene blue counterstain; AFB appear red against a blue background; used to detect mycobacteria in tissue sections and smears.