Cystic Ancient Schwannoma of the Left Thigh: A Rare Presentation in a Middle-Aged Female

Background: Schwannomas are benign peripheral nerve sheath tumors that rarely present with cystic degeneration. Their occurrence in the thigh with attachment to the sciatic nerve is uncommon and can pose a diagnostic challenge. Case Presentation: We report the case of a 53-year-old female with a progressively enlarging, painful swelling over the left thigh for three months. MRI demonstrated a multiloculated cystic lesion in the intermuscular plane of the posteromedial thigh. Excision biopsy revealed a reddish-blue cystic mass attached to the sciatic nerve, measuring 6×5 cm. Histopathological examination confirmed the diagnosis of ancient schwannoma with cystic changes, with free circumferential margins. The patient had an uneventful postoperative recovery and remains under follow-up. Conclusion: Ancient schwannomas, though benign, may mimic malignant tumors due to their atypical imaging features and cystic degeneration. Careful surgical excision with nerve preservation remains the mainstay of management.