A Rare Case of Epstein-Barr Virus Negative Inflammatory Pseudotumor-like Follicular Dendritic Cell Sarcoma Presenting as a Solitary Colonic Mass in a 53-Year-Old Woman; Case Report and Review of Literature

Follicular dendritic cell (FDC) sarcoma is a rare neoplasm that occurs predominantly in lymph nodes. One third of FDC sarcomas happens in extranodal sites. There are 2 morphologic variants of this tumor: conventional and inflammatory pseudotumor (IPT)-like. IPT-like FDC sarcomas are reported mostly in females and usually involve the spleen and liver. In all cases of IPT-like FDC sarcoma the Epstein-Barr virus (EBV) was positive by in situ hybridization except one instance. We report a case of 53-year-old woman who presented with abdominal discomfort. Colonoscopy identified a sessile polypoid mass. Microscopically, there was a prominent lymphoplasmacytic infiltrate. Interspersed among the reactive lymphoid cells were large, pleomorphic stromal cells with marked atypia, irregular and multilobed nuclei, and hyperchromatic smudged chromatin. Immunohistochemical studies demonstrated the atypical stromal cells to be strongly positive for CD10 and D2-40, but negative for CD21, CD23, Clusterin, and epidermal growth factor receptor. EBV-encoded mRNA was negative. A diagnosis of IPT-like FDC sarcoma was rendered. To our knowledge, this is the second case of EBV-negative IPT-like FDC sarcoma reported so far in the literature.