Angiofibroma of Knee Masquerading as Ganglion Cyst - A Rare Case Report

Angiofibroma of soft tissue (AFST) is a rare benign neoplasm characterized by distinctive histopathological and genetic features. It commonly arises in the lower extremities but can present in atypical locations, complicating diagnosis.

A 77-year-old male with a 10-year history of bilateral knee pain and 6-month history of right knee swelling was examined. Physical assessment revealed bilateral knee varus deformity and a palpable, variable-consistency mass in the anteromedial aspect of the right knee. Radiographs indicated severe osteoarthritis and soft-tissue swelling. Magnetic resonance imaging showed cystic collections consistent with a ganglion cyst. Surgical excision exposed a superficial cystic mass and a deeper firm mass, confirmed histopathologically as a ganglion cyst and AFST, respectively. Immunohistochemical tests were negative for epithelial membrane antigen, S-100, and Vimentin. The patient is under regular follow-up with no recurrence in the last 12 months.

AFST should be included in the differential diagnosis of soft-tissue masses. Comprehensive diagnostic evaluations, including detailed imaging and histopathological analysis, are crucial for accurate diagnosis. Surgical excision is effective, with a favorable prognosis and low recurrence risk.