Teaching Case

Complaints of limited stretching of the knee. No past history of trauma.

A 46-year-old male presented with complaints of limited stretching of his knee. The patient’s history revealed no trauma in the past. MRI of the right knee was performed. On a subsequent arthroscopy, a solid intra-articular fibrous tumor was found and completely removed. Histological examination revealed giant cell tumor of the tendon sheath.

Giant cell tumor of the tendon sheath (GCTTS), also called nodular tenosynovitis, is a benign tumor, which occurs in the tendon sheath of the digits or in joints of the extremities. Histologically the tumor consists of proliferation of hystiocytes, multinuclear giant cells, lipid laden macrophages (foam cells) and hemosiderin-laden cells. Owing to the presence of hemosiderin deposition and dense acellular fibrous tissue, low signal intensity within the lesion on both T1- and T2-weighted spin echo MR images is seen. This pattern however is variable and regions of high signal intensity on T2-weighted spin echo MR images may be seen. Because of the variable amount of hemosiderin in GCTTS the tumor shows a lower signal intensity than that of skeletal muscle on T2-weighted and gradient-echo MR images. The differential diagnosis includes pigmented villonodular synovitis and intra-articular ganglion cyst. Pigmented villonodular synovitis shows the same signal intensity as GCTTS on T1- and T2-weighted spin echo MR images, but usually has a more extensive intra-articular involvement with typical frondlike villous masses. It is mostly inhomogeneous and enhances markedly after gadolinium injection. An intra-articular ganglion cyst contains fluid and has always a homogeneous high signal intensity on T2-weighted spin echo MR images, and low to intermediate signal intensity on T1-weighted spin echo MR images.