A long-term survival case of histiocytic sarcoma by surgery alone in a Japanese elderly breast tumor patient

INTRODUCTION: Histiocytic sarcoma (HS) is a rare hematologic malignancy. HS of the breast is extremely rare, and we present a case of an elderly patient with breast HS. CASE PRESENTATION: An 81-year-old woman with unremarkable past medical and family histories presented to our hospital with a palpable mass in her right upper breast. She had noticed a mass in her right breast 3 months before her first visit. Physical examination revealed a mass measuring approximately 30 mm in the right upper quadrant of the breast; there were no cervical or axillary lymphadenopathies. Mammography revealed a high-concentration mass with unclear margins in the upper and outer breast. Ultrasound and magnetic resonance imaging (MRI) revealed a 31 × 23-mm nodule with a relatively clear margin and necrotic sign on the T2-intensified image. A mastectomy was performed upon the patient’s request, and the surgical specimen revealed a 35-mm hemorrhagic mass. The lesion was estrogen receptor-, progesterone receptor-, and HER2/neu-negative. The Ki-67 labeling index was approximately 30%. The immunohistochemical panel showed immune reactivity for the histiocytic markers CD68, CD163, and CD206 and was immune-negative for B lineage, T lineage, Langerhans cells, and keratins. The diagnosis of HS was based on the morphological and immunophenotypic characteristics of the mass. The patient received no systemic therapy and survived for 50 months without recurrence. CONCLUSIONS: Here, we report the case of an elderly patient with rare breast HS. Although the prognosis of HS seems poor, the breast HS was not as poor as expected, since it might have been discovered in the local region before it metastasized.