The marginal zone or centrocyte
-like cells are small to medium-sized lymphocytes with variable nuclear membrane irregularities, resembling a centrocyte
Major Morphologic Features, Immunophenotype, and Molecular/Cytogenetic Features of Small Lymphoid Lymphomas That Involve Extranodal Sites * Lymphoma Type Morphology CLL/SLL Small, round lymphocytes FL Centrocytes and centroblasts PCFCL Centrocytes and centroblasts FL-GIT Same as FL LPL Small lymphs, plasmacytoid lymphs, plasma cells MCL Small, round or cleaved cells LG Variable number of large cells HCL Small lymphs Plasmacytoma Plasma cells MALT Variable morphology, lymphoepitheli- al lesions, centrocyte-like, monocyt- oid, plasma cells Lymphoma Type Immunophenotype CLL/SLL [CD5.
Also challenging may be cases of follicular lymphoma in which there is an admixture of centrocytes and centroblasts (follicular lymphoma, grade 2), which may resemble reactive germinal centers.
12) Diagnosis of follicular lymphoma at extranodal sites requires the same criteria as for nodal disease; namely, the presence of neoplastic centrocytes and centroblasts with characteristic phenotype, usually with coexpression of CD10, CD20, Bcl-2, and Bcl-6.
Grade 3a has a mixture of centrocytes
, while grade 3b lacks centrocytes
and shows a sheet-like proliferation of centroblasts (7).
When naive B-cells (BCL6-, MUM1-, CD 138-) enter the germinal centre, they become centroblasts (BCL6+, MUM1-, CD138-) that subsequently mature into centrocytes
(BCL6+, MUM1-, CD138+) as they undergo immunoglobulin class switching, somatic hypermutation of the immunoglobulin variable genes and mutations of the proto-oncogene BCL6.
The neoplastic cells vary from small to large, showing folding and cleaving of the nuclei, resembling centrocytes
(small- to medium-sized cleaved cells with inconspicuous nucleoli) and centroblasts (large noncleaved cells with vesicular chromatin and several peripheral nucleoli).
2,3) These large B cells included large centrocytes, centroblasts, and B immunoblasts.
4-6) This round, nuclear morphology identifies the centroblasts and immunoblasts characteristic of this lymphoma and distinguishes these cells from the cleaved or irregular nuclear morphology of large centrocytes.
At high magnification, the cells in this case were monotonous, cleaved centrocytes
(Figure 1, B).
Immunostains are helpful, as the centrocytes
and centroblasts of the neoplastic follicles in follicular lymphoma are typically CD10, BCL-6, and BCL-2 positive.
Cases with increased centrocytes
are excluded because they are more likely follicular lymphomas.