Interdigitating dendritic cell tumor: A rare case report with review of literature.

Interdigitating dendritic cell tumor/sarcoma (IDCT) is a very rare and aggressive neoplasm arising from antigen-presenting cells. It usually involves lymph nodes, but extranodal sites can also be involved. Because of the rarity of the disease, consistent standard treatment guidelines have not been established till date. We report a case of a 35-year-old female who presented with right-sided neck swelling and anterior mediastinal mass. Histopathology revealed large mononucleated cells with background of mixed polymorphous inflammatory cells suspicious of Hodgkin's lymphoma. Hence, to confirm the diagnosis, immunohistochemistry was done. Immunohistochemistry revealed that the tumor was CD30 - negative, CD10 - negative, CD2 - negative, leukocyte common antigen - positive, vimentin - positive, and S-100 - positive, diagnostic of IDCT. Patient was treated with eight cycles of cyclophosphamide, doxorubicin, vincristine, and prednisolone regimen chemotherapy followed by involved field radiotherapy and showed dramatic response with complete resolution of mediastinal mass.