Abstract
Soft tissue sarcomas arise infrequently and make up less than 1% of all cancers. An undifferentiated pleomorphic sarcoma (UPS), formerly known as a malignant fibrous histiocytoma, is a malignant subtype of soft tissue sarcoma identified by a lack of specific immunohistochemical markers for lineage differentiation. These tumors are aggressive and enlarge rapidly with an increased risk of metastasis, thus prompt diagnosis, treatment, and post-resection surveillance are imperative. This case report demonstrates an incidental finding of a large undifferentiated pleomorphic sarcoma of the posterior thigh in an 86-year-old male initially evaluated with a bedside ultrasound.