Background:

The low-grade fibromyxoid sarcoma is a rare tumor, described by Evans in 1987 as having a seemingly benign clinical course and histology, but local and distant aggressive behavior; it corresponds to 0.7% of all soft tissue tumors.

Case report:

Forty-nine-year-old female athlete, with a three-month history of pain in the middle left buttock during the race; exploration: 5 x 4 cm, firm mass in the gluteus medius. She underwent resection, with a diagnosis of low histologic grade fibromyxoid sarcoma with positivity only to vimentin. She was subjected to radiotherapy and 10 cycles of chemotherapy. The thoracic tomography was normal at 12 months; at 17 months, PET/CT showed multiple metastatic disease. At present (two years after the diagnosis), she is receiving palliative management and performing moderate exercise.

Conclusions:

Low-grade fibromyxoid sarcoma is a rare tumor and may mimic other soft tissue tumors; recurrences and metastases are described in up to 68% and 40% of cases, respectively.