A Case of Axillary Low-grade Fibromyxoid Sarcoma that was Difficult to Diagnose

Abstract

The patient was a 50-year-old woman. At the age of approximately 18 years, she noticed a small, finger-sized tumor in her left axilla and visited a medical institution ; however, no relevant abnormality was identified. In approximately 2004, the tumor gradually increased in size and began drooping. Thereafter, skin erosion with exudate and odor appeared. She visited our hospital in 2018. A tumor that was slightly larger than an adult's head was found in her left breast. The skin covering the tumor was dark red and showed venous dilatation. A core needle biopsy was performed ; however, no definitive diagnosis was made because of the presence of necrotic tissue. When the clinical and imaging findings were considered, a diagnosis of malignant phyllodes tumor was made and surgery was performed. The tumor was located outside the mammary gland and was partially attached to the latissimus dorsi muscle. The resected specimen weighed 7.4 kg. Macroscopically, the tumor was fibrous with clear boundaries, necrosis in the center, and some self-destruction of the skin. The pathological diagnosis was low-grade fibromyxoid sarcoma (LGFMS). On the basis of intraoperative findings, it was considered that the tumor originated from the axillary soft tissue. No recurrence has occurred 2 years after the surgery. We here report a rare case of LGFMS originating from axillary soft tissue.