Malignant peripheral nerve sheath tumor mimicking post-traumatic hematoma: A case report.

Malignant peripheral nerve sheath tumors (MPNSTs) are rare and aggressive soft tissue sarcomas that can mimic benign lesions. We report the case of a 44-year-old man who developed progressive swelling of the left thigh following a motorcycle accident two months earlier. The initial clinical impression was a post-traumatic hematoma; however, aspiration yielded no fluid. Ultrasonography revealed an irregular, heterogeneous lesion with cystic areas. No vascular flow was detected on color Doppler imaging, whereas superb microvascular imaging (SMI) demonstrated irregular, low-velocity microvascular signals within the solid components. Magnetic resonance imaging (MRI) showed heterogeneous signal intensity, diffusion restriction, heterogeneous enhancement, and extension into the adjacent muscle compartments. Histopathological and immunohistochemical analyses (focal S-100 and Desmin positivity) confirmed a diagnosis of high-grade MPNST. This case emphasizes the importance of considering malignancy in persistent or enlarging post-traumatic soft tissue lesions. Combined evaluation with SMI and MRI may enhance early suspicion of malignancy, enabling timely diagnosis and appropriate patient management.