Synovial hemangiohamartoma presenting as knee pain, swelling and a soft tissue mass: a case report

INTRODUCTION We present a case of a patient with juxtaarticular hemangiohamartoma with a synovial extension associated with hemorrhagic synovitis and recurrent spontaneous hemarthrosis. CASE PRESENTATION A 21-year-old Caucasian woman was admitted to our hospital complaining of pain and swelling at her knee for 6 months. In the magnetic resonance imaging, T2-weighted and fat-suppressed scans revealed a mass with high signal intensity just posterior to the patellar tendon. We performed an excisional biopsy of the mass through an anterior longitudinal incision. Excised material included arterial and venous vascular structures, which were found to be spread among the fat, connective and peripheral nerve tissues microscopically. CONCLUSION Although hemangiohamartomas are not true neoplasms, they may cause knee pain, swelling and hemarthrosis that warrant surgical resection. This lesion, although rare, should be considered in the differential diagnosis, especially in teenagers and young adults.