Objective: Undifferentiated pleomorphic sarcoma (UPS) is rare and affects mainly the elderly. Due to the low incidence and heterogeneous variety of this sarcoma, little is known about the UPS regarding clinical behavior, treatment strategies and prognosis. The objective is to describe the case of a young patient, with a UPS measuring 14 × 11.2 × 8.2 cm, with a 6-month evolution and no metastases.

Case Report: A female patient, 34 years old, reported the presence of nodulation in the left gluteal region for 6 months with progressive growth associated with pain, weight loss of 10 kg in the last 2 months. An anatomopathological study showed a malignant neoplasm of spindle cells and high-grade pleomorphic sarcoma on immunohistochemistry. Neoadjuvant chemotherapy and complete resection of the lesion with subsequent adjuvant radiotherapy were performed.

Results: Since undifferentiated pleomorphic sarcoma has a better prognosis when diagnosed early and in a small size, it is crucial to immediately recognize and assess any enlarged mass and nodule, even though it is a rare diagnosis.

Conclusions: Due to the high rate of recurrence and metastasis, monitoring should be carried out regularly for years after surgical excision.