The presence of back-to-back follicles or nodules (as seen in the upper dermis of Figure 7, A) is not seen in many cases of PCFCL, where there may be confluence of nodules (bottom half of the biopsy specimen in Figure 7, A) or just diffuse effacement with B cells (Figure 7, B) with centrocyte
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.
The histology of FL is characterized by germinal centers of B lymphocytes, predominantly centrocytes
and centroblasts with follicular growth pattern (2,5).
For example, the antiapoptotic protein BCL2 is expressed by benign T cells and mantle zone B cells but is not expressed by benign germinal center B cells (GCBs; centrocytes
and centroblasts), a subset of which must undergo apoptosis for optimal selection of antibody-producing B cells.
USG-guided fine-needle aspiration(FNA) taken from the mesenteric lymph nodes showed lymphocyte predominance, few centro blasts,and centrocytes
in the background of lympho glandular bodies and red blood cells without granuloma and epitheloid cells; which is suggestive of reactive lymphadenopathy.
Reactive lymphadenitis was second most common finding with 13(26%) cases showing predominantly small lymphocytes, transforming lymphocytes, centrocytes
, centroblasts, tingible body macrophages and few histiocytes.
1 FL consists of centrocytes
and centroblasts which originate from germinal centre B cell which usually have a partially follicular pattern.
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.
Histologically, the tumor is composed of large-cells with variable nuclear features, resembling centroblasts, large centrocytes
, or multilobated cells, often with pale or "clear" cytoplasm.
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).
Secondary follicles form when primary follicles react to antigen stimulation and are characterized by a peripheral mantle zone of small mature B cells surrounding a central germinal center made up of antigen-selected centroblasts and centrocytes
that segregate into polarized dark and light zones, respectively, with admixed tingible body macrophages and follicular dendritic cells (Figure 1, C).