Interdigitating dendritic cell sarcoma of lymph node mimicking granuloma: a case report and review of the literature.

Interdigitating dendritic cell sarcoma (IDCS), is an extremely rare neoplasm. We report a case of a 77-year-old man presented with gradual lymph nodes enlargement in inguina, neck and axilla for 6 months. Biopsy revealed that part of the lymph node was replaced by several large granuloma-like nodules composed of mild atypical tumor cells, resembling epithelioid cells. Mitotic figures were hardly found. Immunohistochemistry showed that tumor cells were positive for S-100, CD68 and CD45. Ki-67 labeling index was 5%. To the best of our knowledge, this is the first case of IDCS showing granuloma-like growth pattern with mild atypical tumor cells.