Localized Giant Cell Tenosynovial Tumor Seen in the Knee Joint

Tenosynovial giant cell tumor is a locally aggressive tumor arising from the synovia of the fibrous tissue surrounding the joints, tendon sheaths, mucosal bursas, and tendons. Although it is often to be observed at the hand, localized form is very rare in the knee joint. In this case report, we aimed to present a very rare case of a surgically treated intra-articular giant cell tenosynovial tumor arising from the hoffa’s infrapatellar fat pad of a 19-year-old male patient, by reviewing the literature. The patient we have treated with marginal excision was asymptomatic at the 14th month in the controls and recurrence was not detected. 1. Introduction Tenosynovial giant cell tumor is a locally aggressive tumor arising from the synovia of the fibrous tissue surrounding the joints, tendon sheaths, mucosal bursas, and tendons [1–3]. Tenosynovial giant cell tumor, first described by Jaffe et al in 1941, is also known as pigmented villonodular synovitis [4]. There are localized and diffuse forms. Localized form is usually seen in the palmar region of hand and is rarely seen in the foot [1–8]. Tenosynovial localized giant cell tumor is very rare in the joint [1–3]. In this case report, we aimed to present a very rare case of a surgically treated intra-articular giant cell tenosynovial tumor arising from the tenosynovial tissue of the knee joint of a 19-year-old male patient, by reviewing the literature. 2. Case Report 19-year-old male patient was admitted to our clinic with complaints of swelling and pain increasing with activity in his left knee. The patient had no pain at rest. On the examination of the patient there was a 2 × 3？cm in size swelling that appeared during flexion at the lateral side of the infrapatellar region of the left knee. Lachman, anterior drawer, posterior drawer, and medial and lateral stress tests were negative. Mc Murrey and Apley tests were also negative. The laboratory tests were normal. No abnormal findings were found at the X-ray. A heterogeneous, 3 × 2？cm sized, well-circumscribed lesion localized into the infrapatellar fat pad in the left knee was present at the MR-imaging. The lesion was hypointense on T1-weighted images and hyperintense on T2-weighted images (Figures 1 and 2). Figure 1: Hypointense lesion in infrapatellar region on T1-weighted MRI sequences. Figure 2: Hyperintense lesion in infrapatellar region on T2-weighted MRI sequences. Operation was planned because the lesion was symptomatic. Although the lesion was well-circumscribed, the lesion was heterogeneous, pathologies such as synovial sarcoma could be observed in