Histiocytic sarcoma arising in the liver: a case report and review of the literature

Background: Histiocytic sarcoma (HS) is a rare and controversial hematopoietic neoplasm. The etiology of the disease is unclear and the pathologic diagnosis is challenging. We describe an unusual case of HS arising in the liver of a patient. Case presentation: A 28-year-old female, without pertinent past medical history, presented with an abdominal mass and non-specific symptoms. Abdominal CT and MRI imaging revealed multiple heterogeneous masses in the liver. The patient underwent partial hepatectomy. The specimen consisted of a predominantly gray, solid, moderately firm mass measuring 9.0x6.0x5.0 cm. Histological examination revealed a highly undifferentiated neoplasm comprised of markedly atypical large cells with eosinophilic to vacuolated cytoplasm, showing occasional hemophagocytosis. Immunohistochemistry showed strong positive tumor staining for CD4, CD68, CD163 and lysozyme, and negative staining for CD3, CD5, CD20, CD138, and CD30. Conclusion: Here we discuss different diagnostic considerations and establish a final diagnosis of HS with integration of histological, immunohistochemical and genetic testing. This case provides a systematic diagnostic approach to HS.