[Interdigitating dendritic cell sarcoma successfully treated with ABVD therapy in which serum CEA levels correlated with disease activity].

Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare neoplasm of spindle to ovoid cells with phenotypic features similar to those of interdigitating dendritic cells. No standard therapy for advanced IDCS has yet been established. According to past reports, CHOP-like regimens are often chosen as primary therapy. Herein, we report a case with advanced IDCS, for which ABVD achieved remarkable clinical improvement and serial CEA levels correlated with disease status. A 76-year-old man presented with general fatigue and pancytopenia with CEA elevation. Colonoscopy showed erosion and polyps in the colon. FDG-PET showed marked abnormal accumulation throughout the bone marrow. Pathologically, polyps of the colon and IDCS of the bone marrow were diagnosed. Although the patient received CHOP as initial therapy, clinical improvement was not significant. Subsequently, six cycles of ABVD resulted in remarkable regression of both the colonic polyps and the bone marrow infiltration. Moreover, the patient was transfusion-free after ABVD. In addition to these clinical responses, serial CEA levels normalized. Our case highlights the efficacy of ABVD for IDCS and serial CEA measurements might reflect treatment efficacy.