Non-Hodgkin's lymphoma involving bilateral breasts.

We describe here two cases of diffuse large cell type non-Hodgkin's lymphoma affecting the bilateral breasts. The contralateral tumor in one case appeared 17 months after the first mastectomy, whereas the bilateral tumors occurred concurrently in the other patient who was pregnant and showed widespread dissemination at initial presentation. Lymphoma cells from both cases showed the mature B-cell immunophenotype and had rearrangements of the BCL6 gene. Both patients developed progressive disease despite chemo-radiotherapy and died of leukemic manifestations. There were no apparent pathological features of lymphomas of mucosa-associated lymphoid tissue origin.