A Rare Cause of Anterior Knee Pain: Radiological and Histopathological Analysis of a Prepatellar Subcutaneous Venous-Type Angioleiomyoma

Angioleiomyoma is a rare benign tumor arising from the smooth muscle cells of vascular walls, with prepatellar localization being exceptionally uncommon. We present the case of a 30-year-old female patient with anterior knee pain and swelling, without a history of trauma or systemic disease. Physical examination revealed a mobile, well-circumscribed subcutaneous mass. Ultrasonography demonstrated a hypoechoic nodular lesion, and magnetic resonance imaging further characterized it as a well-defined soft tissue mass with iso-hyperintense T1-weighted and hyperintense proton density (PD) signals, exhibiting significant gadolinium enhancement. Surgical excision was performed, and histopathological analysis confirmed the diagnosis of a venous-type angioleiomyoma, with smooth muscle actin (SMA)-positive and desmin-positive spindle cells, lacking atypia or mitotic activity. Postoperatively, the patient's symptoms resolved completely, with no recurrence. Given the rarity of prepatellar angioleiomyomas, their diagnosis can be challenging due to overlapping radiological features with other subcutaneous tumors, including hemangiomas and glomus tumors. This case underscores the importance of integrating clinical, radiological, and histopathological findings for accurate diagnosis and appropriate management. Early recognition and surgical excision are essential for symptom relief and favorable outcomes.