A Rapidly Progressing Lower Extremity Soft Tissue Sarcoma in an Adolescent Patient.

Soft tissue sarcomas (STSs) are rare malignant tumors of mesenchymal origin with heterogeneous histologic subtypes and variable clinical behavior. Although STSs most commonly arise in the extremities, rapidly progressive sarcomas involving the distal lower extremity in adolescents have not been well documented. We report a case of an STS in a previously healthy adolescent female whose initial presentation was presumed to be a muscle strain. Over a three-month period, her symptoms worsened with progressive enlargement of a calf mass and development of widespread metastatic disease. This case highlights the importance of maintaining suspicion for malignancy in rapidly enlarging soft tissue masses, with timely referral to specialized sarcoma centers for further evaluation.