A case of primary B-cell lymphoma of the breast. Light and electron microscopy, and immunologic cell markers.

A case of primary non-Hodgkin's lymphoma of the breast was studied with light and electron microscopy and for immunologic cell markers. With light microscopy, the tumor was seen to be a poorly differentiated lymphocytic lymphoma, diffuse, according to Rappaport's classification. With electron microscopy, the tumor was seen to consist of a cytologically uniform cell population. The cells were characterized by irregularly shaped nuclei with infrequent cytoplasmic projections and "microvilli-like" structures, mimicking small cleaved follicular center cells. The immunologic cell marker study showed that the cells were positive for surface IgA and HLA-DR antigen; negative for SRBC receptors, Leu 1, Leu 2a, and Leu 3a antigens. The collective evidence indicated the tumor was of B-cell origin.