Primary Follicular Dendritic Cell Sarcoma of Breast: 2 Further Cases with Review of the Literature.

Follicular dendritic cell sarcoma (FDCS) is a tumor derived from antigen-presenting cells and can occur within lymphoid tissue or at extranodal sites. FDCS of the breast is remarkably rare, with only 4 cases previously reported in literature. FDCS appears grossly as a well-circumscribed, firm mass with a grey-yellow surface, areas of necrosis, and histologically comprises of spindled, oval, or epithelioid cells with intensely eosinophilic cytoplasm. Immunohistochemistry plays a key role in its diagnosis. Here we describe 2 cases of FDCS of breast in 2 women aged 70 and 35 years old, who presented with a palpable lump in the breast. One patient had concomitant invasive ductal carcinoma as well. We highlight the key histopathological and immunohistochemical features of the tumor.