Answer: Burkitt’s lymphoma

Histology: This is a primitive B cell neoplasm which essentially overruns the breast stroma. There are sheets of medium sized cells with nuclear diameter similar to that of a macrophage. The nuclei are squared off, have coarse chromatin, and multiple nucleoli. The cytoplasm has a deep blue appearance with fine lipid vacuoles. Mitotic activity is very high, and there are tingible body macrophages yielding a “starry sky” pattern. By immunohistochemistry, the neoplastic cells label for CD20, but not for Bcl 2. The Ki-67 proliferation rate is near 100%. These are the typical features of Burkitt’s lymphoma.

Discussion: Basal-like breast carcinoma is high grade cancer which typically affects young patients; however, it is usually not bilateral, often shows squamous features, and would demonstrate epithelial differentiation by immunohistochemistry. Solid variant lobular carcinoma would have rounder nuclei with intracytoplasmic mucin, and would also demonstrate epithelial differentiation by immunohistochemistry. Small cell carcinoma would show greater nuclear molding, less prominent nuclear membranes, and also demonstrates epithelial differentiation by immunohistochemistry.

Burkitt’s lymphoma is characterized by rearrangements involving the MYC gene on chromosome 8q24. These lymphomas are often extra nodal. The three classic types are endemic, which predominates in Africa, affects children, and often involves the jaws and bones; sporadic, which typically affects children and young adults, and frequently involves the ileum; and HIV-associated.