Diffuse large B-cell lymphoma arising in a composite lymphoma with biclonality by flow cytometry and one monoclonal band by PCR

Abstract

Composite lymphoma (CL) refers to the presence of two or more distinct types of lymphomas in a single organ or tissue. CL is an infrequent finding and may be due to the existence of two genetically related neoplasms, i.e. transformation of a single lymphoma into another lymphoma, or be due to the presence of two clonally unrelated lymphomas. CL composed of more than two lymphomas is even rare. Herein we describe a case of diffuse large B-cell lymphoma (DLBCL) arising in a CL of follicular lymphoma (FL) and small lymphocytic lymphoma (SLL) in an inguinal lymph node of an 85 year old woman. The three lymphomas were morphologically and immunophenotypically distinct while flow cytometry detected two monoclonal B-cell populations. Karyotyping and Polymerase Chain Reaction (PCR) for B-cell clonality each detected a single monoclonal B-cell population. The morphology findings may suggest DLBCL being transformed from FL while Richter transformation from SLL appears to be less likely in our case. Due to the single clone by chromosome study and PCR study, the precise relationships of the three lymphomas are unknown.

Keywords: Composite lymphoma; PCR; bi-clonality; diffuse large B-cell lymphoma.

Figure 1

Low magnification of the lymphoid infiltrate (× 100).

Figure 2

High magnification shows diffuse sheets of large atypical lymphoid cells with centroblast morphology (× 400).

Figure 3

Histogram of the flow cytometry study demonstrated two populations of monoclonal B-cells. The gated events in red are lambda light chain restricted B-cells expressing CD19, CD20, and CD10 while gated events in green are lambda light chain restricted B-cells expressing CD19, CD20, CD5, CD43 but negative for CD10.

Figure 4

Capillary electrophoresis based PCR study showed one restricted monoclonal band.