Pulmonary Mass as the First Clinical Manifestation of Histiocytic Sarcoma with Multi-Organ Involvement: A Case Report and Review of the Literature.

Histiocytic sarcoma is a malignant neoplasm with cells showing morphologic and immunohistochemical features of histiocytes. The lung and stomach are rare sites of involvement, and few have been reported in the existing literature. We report a 72-year-old woman with primary histiocytic sarcoma involving the right lung, stomach, and bilateral adrenal glands. Computed tomography revealed a large heterogeneous mass in the upper lobe of the right lung, regional lymphadenopathy, and masses within the bilateral adrenal glands. Gastric involvement was discovered via polypectomy during a routine gastric endoscopy. Morphologically, the lung and stomach specimens showed sheets of large and spindle cells with increased mitotic figures. Immunohistochemical staining revealed CD163, CD68, and CD4 expression in the lung tumor and CD163 and CD4 in the gastric tumor. The patient deteriorated rapidly and died of a pulmonary infection two months after diagnosis. Surgical resection remains the most effective treatment. However, for those with advanced disease, systemic chemotherapy alone may be the only available option, but the outcomes are variable. Advancements in targeted therapy are needed to improve treatment outcomes for patients with multi-organ involvement of histiocytic sarcoma.