[A Case of Stromal Sarcoma of the Breast Showing Rapid Increase].

An 83-year-old woman visited our hospital with a mass on her right breast mass. Breast ultrasonography revealed a tumorous lesion approximately 30mm in diameter in the right E region. Fibrous tumor was suspected from core needle biopsy. Since surgery for definite diagnosis was not desired, she was followed. Seven months after the first visit, skin redness, pain, and rapid increase in tumor size was consciously recognized, which prompted a reconsultation. The tumor diameter rapidly increased to 74 mm, and a total right mastectomy was performed as a semi-emergency procedure. Necrotic and hemorrhagic lesions were mixed in a mottled state in the cleaved surface of the excised specimen, and the pathological diagnosis was stromal sarcoma mainly comprising of fibrosarcoma components. Stromal sarcoma of the breast lacks the epithelial component of a malignant phyllodes tumor, and effective systemic therapy has not been established; therefore, cases with local recurrence or distant metastasis result in poor prognosis. Since we encountered a case of stromal sarcoma of the breast that showed a rapid increase after several months, we will provide a report with some literature consideration.