Metastatic Histiocytic Sarcoma with Secondary Involvement of the Skin: A Case Report.

Histiocytic sarcoma (HS) is a rare malignant neoplasm of presumed hematopoietic origin, showing morphologic and immunophenotypic evidence of histiocytic differentiation. A 61-year-old woman presented with an abdominal mass. She had a history of HS in both adrenal glands. The tumour cells of the left adrenal gland were very large epithelioid cells with abundant eosinophilic cytoplasm and large, round-to-oval nuclei. Similarly, the cutaneous lesion of the skin was composed of polygonal cells with well-defined cell borders and high nuclear/cytoplasm (N/C) ratios. Immunohistochemically, both tumours were positive for histiocyte-associated antigens but negative for epithelial, melanocyte, lymphoid, dendritic, and Langerhansl nuclei. Similarly, the cutaneous lesion of the skin was composenose correctly. It is important to recognise the morphological features and immunohistochemical characteristics of metastatic cells in order to achieve accurate diagnoses.