Primary high-grade soft-tissue sarcoma of the buttock: a rare but distinct clinical entity.

Objective: Sarcoma arising in the region of the buttocks is a rare entity and therefore no consensus regarding management exists in the literature. Methods: 16 patients diagnosed with localized, non-metastatic primary soft-tissue sarcoma (STS) in the buttock area, who were consecutively treated between 2005 and 2013, were retrospectively evaluated for the rate of local control, distant metastases and overall survival. Results: Most tumours were classified as high grade (87.5%). The average time between the appearances of symptoms to diagnosis of sarcoma was 4.5 months. At the end of the observation period, 7 (44%) patients were alive without signs of progressive disease, 37.5% patients died as the disease progressed, 13 patients were free of disease and 3 (19%) patients were alive with signs of progressive disease. Seven (44%) patients developed local recurrence. Six (37.5%) patients developed distant metastases. The lung was the most common site of distant failure (four patients); other sites were the liver as well as the adrenal gland and kidney (one patient). Four patients had both distant and local progression, three patients experienced isolated local recurrence and two patients developed isolated distant metastases. 5-year local recurrence-free survival was 58% and 5-year distant metastases-free survival was 63%. Conclusion: It is unclear whether to subsume STS of the buttock under the rubric of pelvic tumours or tumours of the lower extremity. Either way, STS of the buttock seems to be characterized by local control, freedom from distant relapse and survival, which is inferior to accepted standards for either pelvic or lower extremity sarcomas. To improve this poor outcome, oncologists are encouraged to regard sarcoma of the buttock as a distinct clinical entity and to devise innovative therapeutic strategies accordingly. Advances in knowledge: Sarcoma of the buttock area should possibly be regarded as a distinct entity.