Synchronous small lymphocytic lymphoma and metastatic breast carcinoma in axillary lymph nodes: Preservation of follicular architecture only in the portions of affected lymph nodes involved by metastatic carcinoma.

We present a case of metastatic ductal carcinoma of breast with the incidental discovery of small lymphocytic lymphoma (SLL) in regional axillary nodes. The co-occurence of metastatic carcinoma and low-grade lymphoma in lymph nodes is rare but well recognized. However, in this case, in the lymph nodes in which sizeable metastatic carcinoma deposits were present, the follicular structures between the sinusoidal carcinomatous infiltrates were preserved, whereas the uninvolved portions of the nodes were overrun by SLL. This is the first description of this phenomenon. We suggest that further cases displaying this previously unpublished pattern are collated in order that we may begin to investigate the underlying etiological mediators.