Page 354 - Concise Pathology for Exam Preparation ( PDFDrive )

12 Haematology 339

(f) Pan B markers, CD19, CD20, CD10 and BCL6 (transcription factor required for
follicular centre formation) and BCL2-positive
(g) Majority of tumours have a characteristic translocation t(14;18).
(h) Natural course of disease is prolonged (median survival from 7 to 9 years); but not
easily curable due to increased levels of BCL2, which blocks apoptosis to increase
survival of tumour cells.
(i) In 40% patients, follicular lymphomas progress to a diffuse large B-cell lymphoma.
3. Mantle cell lymphoma
(a) Four percent of all NHLs
(b) Present with lymphadenopathy and involvement of bone marrow, liver, spleen and
bowel (multifocal submucosal nodules resembling polyps called lymphomatoid
polyposis), mainly in older males
(c) Lymph nodes show diffuse or vaguely nodular pattern of effacement
(d) Composed of B cells that resemble the cells in the mantle zone of normal lymphoid
follicles
(e) Tumour cells are slightly larger than normal lymphocytes with an irregular nucleus
and inconspicuous nucleoli and express IgM, IgD, CD19, CD20 and CD5.
(f) Translocation (11;14) is commonly seen and results in fusion of Cyclin D1 gene on
chromosome 11 to the IgH locus on chromosome 14 inducing dysregulation of
expression of Cyclin D1 and increased levels of the same.
(g) Aggressive with a median survival of 3–5 years
4. Diffuse large B-cell lymphoma
(a) Accounts for 50% of adult NHLs
(b) Median age 60 years; slight male predominance
(c) This category includes several forms of NHL, which share the following features:
(i) B-cell phenotype
(ii) Diffuse growth pattern
(iii) Aggressive nature (disseminate widely)
(d) Pan B-cell markers positive along with surface IgM and IgG with variable expres-
sion of CD10.
(e) Tumour cells are largely composed of cells that resemble centroblasts (3–4 times
the size of resting lymphocytes, round, irregular-cleaved nuclear contours, dis-
persed chromatin, distinct nucleoli and moderate pale cytoplasm) as well as a few
cells that resemble immunoblasts (large round to multilobated vesicular nucleus,
1–2 centrally placed prominent nucleoli and pale to intensely staining abundant
cytoplasm).
(f) Some patients have t(14;18); these tumours may represent ‘transformed’ follicular
lymphomas.
(g) A few cases show rearrangements/mutation in BCL6 gene leading to inappropriate
increase in BCL6 protein.
(h) Fatal if untreated; complete remission can be achieved in 60–80% patients by
combination chemotherapy.
(i) Several clinicopathological subtypes:
(i) Diffuse large B-cell lymphoma that arises in the setting of AIDS and iatrogenic
immunosuppression
(ii) Diffuse large B-cell lymphoma arising in the posttransplant setting
(iii) Kaposi Sarcoma herpes virus (KSHV) or Human herpes virus type 8 (HHV-8) as-
sociated ‘primary effusion lymphomas’ in the pleura, pericardium or peritoneum
(iv) Mediastinal large B-cell lymphomas (arise in young females and frequently
spread to abdominal viscera and central nervous system)
5. Burkitt lymphoma
(a) This is a high-grade, non-Hodgkin lymphoma having small noncleaved cells.
(b) Endemic in some parts of Africa and sporadic in the United States.
(c) EBV plays an important aetiological role.
(d) Majority of the cases occur in children; usually in extranodal sites.
(e) In African patients, involvement of mandible and maxillary bones manifests with
deformity, loosening of teeth and proptosis with loss of vision.

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