Monoclonal proliferation of germinal center cells (incipient follicular lymphoma) in an axillary lymph node of a melanoma patient.

A monoclonal proliferation of germinal center cells within a lymph node follicle was incidentally discovered during the staging surgical procedures in a patient with Clark III-level cutaneous melanoma. In one of the 19 axillary lymph nodes examined, we identified a single morphologically atypical lymphoid follicle, predominantly composed of medium-sized cells and immunoreactive for B-cell antigens and for the markers of germinal center origin CD10 and bcl-6. A monoclonal rearrangement of the immunoglobulins heavy chains (IgH) was documented by polymerase chain reaction after laser capture microdissection. The cells of the aberrant follicle expressed the bcl-2 protein at higher levels than the surrounding T lymphocytes in the absence of bcl-2 gene rearrangement. We propose for this lesion the designation of incipient follicular lymphoma. The present findings also confirm the previously reported association between melanoma and lymphoproliferative disorders.