24
Lymph Nodes: Cytomorphology and Flow Cytometry
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Fig. 24.21 Comparison of small and medium-sized B-cell
lymphomas. (A) Mantle cell lymphoma: small cleaved cells. (B) Follicular
lymphoma: polymorphous mixture of cells. (C) Small lymphocytic lymphoma:
round cells with blocky chromatin and occasional prolymphocytes.
(D) Marginal zone lymphoma: round cells with abundant pale cytoplasm
(Papanicolaou x OI).
Fig. 24.22 Comparison of small and medium-sized B-cell lymphomas.
(A) Mantle cell lymphoma: small cleaved cells. (B) Follicular lymphoma:
polymorphous mixture of cells. (C) Small lymphocytic lymphoma: round
cells with blocky chromatin. (D) Marginal zone lymphoma: round cells with
abundant pale cytoplasm, villous lymphocytes present with cytoplasmic
projections at one end of cell (arrow) (Diff-Quik x OI).
Detection of BCL-2 oncoprotein expression by immuno-
histochemistry is not useful diagnostically, since it is not only
present in reactive lymphocytes in benign hyperplasias but also
in other lymphomas, such as MZL and SLL.
Key features of low-grade follicular lymphoma
(Grades 1 and 2)
• Range of cell sizes;
• Many cleaved cells;
• CD10+, CD5- B cells;
• Light-chain restriction;
• BCL-6-positive; and
• t(14;18).
M arginal Zone/M ALT Lym phom a
Clinical
The normal marginal zone consists of the area just peripheral
to the mantle zone of a secondary follicle. It is best appreciated
in the spleen and is not easy to see in extra-abdominal lymph
nodes. MZL is a low-grade B-cell lymphoid neoplasm that shows
differentiation into either monocytoid B cells or plasma cells,
theoretically similar to the differentiation of normal marginal
zone B cells.129
Extranodal MZL is also known as lymphoma of MALT,
although it may occur in sites that are not usually thought of
as mucosal-associated.130 Some low-grade MALT lymphomas
may remain localized for a long time or have a long interval to
relapse. At times it may be difficult distinguishing benign lym-
phoid proliferations from early MALT lymphoma, such as those
occurring in the bronchial or gastric mucosa. Cases of mono-
clonal B-cell proliferations in the stomach with microscopic fea-
tures of MALT-type lymphoma can be cured by antimicrobial
eradication of
Helicobacter.131
In the stomach, but not in other
anatomic sites, prominent lymphoepithelial lesions are fea-
tures of MALT lymphoma.131 FNA would not be able to give this
information, although most of these cases would be detected by
endoscopic biopsy rather than cytologic methods.
Cytomorphology
Aspirates for MALT/MZL contain a monomorphic popula-
tion of small to medium-sized cells with condensed chroma-
tin and indistinct nucleoli together with a small number of
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