Primary Histiocytic Sarcoma Presenting as a Breast Mass: A Case Report

Histiocytic sarcoma is a rare hematologic malignancy, with very few cases of primary histiocytic sarcoma of the breast described in English scientific literature.Herein, we describe a case of primary histiocytic sarcoma of the breast in a 75-year-old woman, with no clinical history of malignant tumors, who presented with a palpable solitary breast mass.Microscopically, the resected breast mass showed large pleomorphic cells, some multinucleated giant cells, and admixed inflammatory components.The pleomorphic tumor cells further showed a diffuse, noncohesive growth pattern, an abundant eosinophilic cytoplasm, and strong and diffuse immunoreactivity for cluster of differentiation (CD) 68 and CD163.Furthermore, a whole-body positron-emission tomography/computed tomography using deoxy-2-[ 18 F]fluoro-D-glucose performed after surgery showed no other masses or lesions.After surgical excision, the patient was followed up, and no evidence of tumor recurrence or metastasis was noted.