Attending Doctor MacKay Memorial Hospital Taipei, Taipei, Taiwan (Republic of China)
Case Diagnosis: Undifferentiated pleomorphic sarcoma of the right thigh, grade III (FNCLCC), stage IIIB (T4N0M0).
Case Description: A 72-year-old man presented to a rehabilitation outpatient clinic with a painless, progressively enlarging right medial thigh mass over several weeks. Physical examination revealed a firm, deep mass measuring approximately 20 × 10 × 5 cm in size. Targeted musculoskeletal ultrasound revealed a large mixed solid-cystic mass exceeding 15 cm in length, located deep to the gracilis muscle, with a heterogeneous internal architecture and marked vascularity. These sonographic findings prompted early suspicion of malignancy and led to expedited referral for definitive diagnosis. Subsequent MRI confirmed a large heterogeneous mass beneath the gracilis and adductor muscles, suspicious for sarcoma. PET showed no evidence of metastatic disease. The patient underwent tumor excision, and histopathology confirmed undifferentiated pleomorphic sarcoma, grade III (FNCLCC), stage IIIB (T4N0M0). At the latest follow-up (January 2026), the patient remained ambulatory with an ECOG performance status of 1.
Discussions: This case highlights the value of ultrasound-based diagnostic decision-making in rehabilitation settings when evaluating atypical deep soft-tissue masses. Sonographic features, including large size, deep fascial location, heterogeneity, and rich vascularity, served as actionable warning signs that shifted clinical reasoning toward a diagnosis of malignancy. The case suggests a reproducible ultrasound-based diagnostic window during which earlier tissue confirmation may be considered, potentially shortening diagnostic delay in aggressive soft-tissue tumors. Establishing a structured ultrasound database in rehabilitation settings could provide the foundation for future AI-assisted malignancy risk stratification and outcome-oriented research.
Conclusions: Early recognition of malignant-appearing ultrasound features by rehabilitation physicians may facilitate timely referral or biopsy decisions and help define a clinically actionable diagnostic window before advanced imaging, with potential implications for preserving function without delaying oncologic care.
