Histiocytic Sarcoma of Colon - A Rare Entity

INTRODUCTION: Histiocytic sarcoma (HS) is a very rare malignant neoplasm of unknown etiology which is not a true sarcoma. It shows similar morphological and immunohistochemical features of mature histiocytes. Most cases involve the extra nodal sites, most commonly the skin, soft tissue, intestinal tract. The clinical presentation of HS is related to the organs involved. HS is an aggressive neoplasm with poor prognosis and lack of standard treatment guidelines. CASE REPORT: We are presenting a case of HS of sigmoid colon in a 33-year-old male patient. The patient had a 3 month history of abdominal pain, bloating and intermittent constipation associated with several episodes of hematochezia. He underwent low anterior resection with wide en bloc lymph node dissection. Detailed histopathological and Immunohistochemical examination of resected specimen led to the diagnosis of Histiocytic sarcoma of sigmoid colon. CONCLUSION: HS is a rare malignant neoplasm with histiocytic differentiation. Patients with localized resectable disease treated with surgery with or without adjuvant radiotherapy while patients with multifocal disease are treated with combination systemic chemotherapy regimens. Keywords: contrast enhanced computed tomography, dendritic cell neoplasm, hematochezia, Histiocytic sarcoma, histiocytic proliferation, melanoma, monocytic leukemia, non Hodgkin lymphoma, undifferentiated large cell carcinoma.