A rare case of peripheral nerve sheath tumor in the inner thigh: Diagnostic approach, management, and clinical implications—A Case report

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft-tissue sarcomas arising from peripheral nerve sheaths, most frequently encountered in the trunk and proximal limbs. Their occurrence in the medial compartment of the thigh, particularly with deep intramuscular extension, is exceptionally uncommon. We report the case of a 50-year-old man with a long-standing history of chronic smoking<b>,</b> who presented with a 6-month history of progressive medial-thigh pain, hypoesthesia, and a rapidly enlarging mass<b>.</b> MRI demonstrated a deep, heterogeneous soft-tissue lesion within the adductor magnus muscle<b>,</b> raising suspicion for a malignant neurogenic tumor<b>.</b> Core biopsy and immunohistochemistry confirmed a high-grade MPNST<b>,</b> characterized by marked cytologic atypia, high mitotic index, and loss of H3K27me3 expression<b>.</b> The patient underwent wide surgical excision<b>,</b> achieving an R0 resection margin<b>.</b> Postoperative recovery was uneventful, with preservation of limb function<b>.</b> At 6-month follow-up<b>,</b> MRI showed no evidence of local recurrence or metastasis<b>.</b> This case highlights a rare intramuscular MPNST of the inner thigh<b>,</b> underlining the importance of correlating MRI features with histopathology and immunohistochemistry to differentiate malignant from benign neurogenic lesions. Early biopsy, accurate IHC profiling, and complete resection remain critical for optimal management of these aggressive tumors.