Interdigitating dendritic cell sarcoma of the ileum recurred in multiple lymph nodes and duodenum three years after operation without chemotherapy

Neoplasms derived from interdigitating dendritic cell are extremely rare. Here we describe a case of a 47-year-old man with interdigitating dendritic cell sarcoma (IDCS) in the ileum. He was admitted to a hospital due to ileus. The ileal tumor, measuring 2 cm, was detected and resected with regional lymphadenectomy. At that time, a pathologic diagnosis of malignant peripheral nerve sheath tumor was made. The patient, who was not treated with chemotherapy, showed no signs of recurrence. After three years, we detected cervical lymphadenopathy and multiple duodenal masses in the patient in our hospital. Oval to spindle-shaped atypical cells, which resembled ileal tumor cells, infiltrated into the lymph node and duodenum. Immunohistochemical staining of these three lesions revealed positivity of S100 protein and several macrophage-related antigens. Based on the histologic and immunohistochemical analysis, the histopathologic diagnosis of IDCS was confirmed. To our knowledge, five cases of IDCS arising in the intestinal tract have been reported to date, and only one case, treated with both surgery and chemotherapy, led to remission. This is the first case that has a comparatively favorable prognosis without chemotherapy after surgery.