Ancient Schwannoma with Hemorrhagic Degeneration Causing Chronic Intramuscular Hematoma: A Case Report

INTRODUCTION: The value of this manuscript is that it highlights a common diagnostic challenge facing orthopedic surgeons, involving the reality that both benign and malignant soft-tissue tumors can present as large cystic masses masquerading as a hematoma. This is the first report of its kind to describe a schwannoma presenting as such a large hematoma in the thigh. CASE PRESENTATION: A 64-year-old male presented with 2 days of worsening pain over a left posterior thigh mass that was enlarging for 12 years. Imaging demonstrated a cystic mass. 1.8L of serosanguinous fluid was aspirated and cytology was negative for malignancy, suggesting chronic hematoma. The fluid reaccumulated, indicating surgical management. Histopathology revealed a hemorrhagic ancient schwannoma. CONCLUSION: Without history of trauma or anticoagulation, intramuscular hematoma should be a diagnosis of exclusion. Burden of proof is high to rule-out a neoplastic process masquerading as fluid collection. Biopsies should be taken and schwannoma with ancient change and cystic degeneration should be considered.