Omental Histiocytic Sarcoma: A Case Report

ABSTRACT

We report a case of perigastric histiocytic sarcoma (HS) involving the lesser omental sac in a 30-year-old man. HS is an exceedingly rare malignancy of mature tissue histiocyte. The tumor was a multi-lobulated, bulging enhancing mass in the lesser omentum with metastasis to lymph nodes and liver. The tumor consisted of diffuse non-cohesive proliferation of pleomorphic large oval to round neoplastic cells with giant cells showing vesicular chromatin and ample eosinophilic cytoplasm. In some areas, the tumor cells showed spindling with elongation of the nuclei and cellular shapes. Many of the tumor cells, especially giant forms contained phagocytosed lymphocytes. Immunohistochemical analysis of the tumor cells showed expression of leukocyte common antigen, CD68, lysozyme, vimentin, CD4, and CD163. Ki-67 index was 50-60%. After the operation, he was treated with chemotherapy, but the response was poor.