Page 353 - Concise Pathology for Exam Preparation ( PDFDrive )

338 SECTION II Diseases of Organ Systems

• Nuclear chromatin is condensed with inconspicuous nucleoli.
• Nuclear membrane may be convoluted or cleaved.
• Some transform to aggressive diffuse large B-cell lymphoma or prolymphocytic lymphoma.
• Precursor B cells are Tdt (terminal deoxytransferase) and CD19-positive immature B
cells (variable expression of other B-cell markers).
• Precursor T cells are Tdt-positive immature T cells (CD2-, 7-positive and variable ex-
pression of other T-cell markers).

Karyotype
• Ninety percent have nonrandom karyotypic abnormalities
• Hyperdiploidy (.50 chromosomes) most common; associated with a good prognosis
• Poor outcome in pre-B-cell tumours is associated with translocation involving the MLL
gene on chromosome 11q23 or Philadelphia chromosome positivity.
• Fifty-five to sixty percent of pre-T-cell tumours have activating point mutations in
NOTCH1 (transmembrane receptor whose activity is essential for normal T-cell devel-
opment, ie, proliferation and survival of pre-T cells).

Mature Peripheral B-Cell Malignancies
1. Small lymphocytic lymphoma (SLL)/chronic lymphocytic leukaemia (CLL)
(a) CLL is diagnosed when there is persistent peripheral blood lymphocytosis exceed-
3
ing 4000 cells/mm .
(b) SLL is essentially a nodal disease (CLL and SLL are morphologically and genotypi-
cally similar; differ only in terms of peripheral blood involvement, in the absence
of which, a diagnosis of SLL is rendered).
(c) CLL more common than SLL in the western world
(d) Both CLL and SLL uncommon in Asia
Pathophysiology:
• Neoplastic B cells suppress normal B-cell function resulting in hypogammaglobu-
linaemia.
• Simultaneously, 15% patients develop auto antibodies against their own RBCs.
• Tumour cells displace the normal marrow elements leading to anaemia, neutropenia
and thrombocytopenia.
Morphology:
• Diffuse effacement of the lymph node architecture by sheets of small round lympho-
cytes (tumour cell is a resting lymphocyte with a dark staining nucleus and scanty
cytoplasm showing minimal cytological atypia and mitoses)
• Absolute lymphocytosis in the peripheral blood with involvement of bone marrow,
liver and spleen seen in almost all cases
• Neoplastic lymphocytes are fragile and frequently disrupted during preparation of
smears; thus, labelled smudge cells
• Neoplastic cells are mature B cells expressing pan B-cell markers CD19, CD20, CD23
and surface immunoglobulin heavy and light chains along with CD5
• Fifty percent patients have karyotypic abnormalities, eg, trisomy 12 and deletions of
chromosome 11 and 12.
2. Follicular lymphoma
(a) More common in the western world than in Asian population
(b) Affects older age group
(c) Presents as painless generalized lymphadenopathy with or without visceral in-
volvement
(d) Lymph nodes effaced with a nodular appearance
(e) Tumour cells resemble normal follicular centre B cells (centrocyte like with cleaved
nuclear contours or nuclear infoldings, coarse chromatin and scanty cytoplasm).
A few centroblast-like cells that have vesicular chromatin, several nucleoli and
moderate cytoplasm, also seen.

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