Age (years)/ gender/side 34/NS NS 54/M/R NS/L, 20/F/L NS 4 Authors/year Jaﬀe et al., 1941 [1] Granowitz et al., 1976 [3] Present et al., 1986 [9] Jelinek et al., 1989 and 1994 [5, 6] Kay et al., 1996 [7] 11/M/R Abdelwahab et al., 2002 [2] Sami et al., 2003 [11] Maheshwari et al., 2007 [8] Riccio et al., 2007 [10] Hepp et al., 2008 [4] 63/F/R 26/F/L 17/F/L 18/M/L 36/M/L 28/F/L Clinical presentation Mass more than 3 years, but no limitation of range of motion NS Pain with moderate joint eﬀusion but a palpable mass × 4 years. There was a lytic lesion in the tibia Swelling without limitation of range of motion × 18 months. Also had a metachronous lesion in the wrist about 18 months prior Increasing swelling and recent-onset pain with limitation of range of motion × 2 years. Also had associated Sjogren’s syndrome Worsening pain and swelling with no limitation of range of motion × 2 months Slowly enlarging mass × 3 years Pain with jogging × 2 years Swelling and pain with jogging × 1 month Swelling and pain × 4 weeks. History of trauma 13 years previously with excision of a similar mass (histologically read as PVNS) in the same location Size >5-6 cm NS NS NS 3.5 × 8.0 cm 5.0 × 3.5 × 2.0 cm 4.5 × 3.0 × 2.5 cm 5.6 × 3.8 × 3.5 cm 6.1 × 3.5 × 3.4 cm 3.5 × 6.5 cm Case Reports in Medicine Treatment Outcome NS NS NS Arthroscopy, followed by incisional biopsy, resection of mass and curetting and cementing of tibial lesion Open biopsy, followed by wide resection and tenodesis of involved tendons Resection of entire mass with repair of resected tendon Open biopsy, followed by marginal excision Open biopsy, followed by marginal resection Marginal resection NS NS NS NS DF × 12 months DF × 18 months DF × 27 months DF × 2 years DF × 18 years DF × 30 months Table 1: Giant cell tumor of the pes anserine bursa (extra-articular pigmented villonodular bursitis): a review of literature. 4.0 × 4.0 × 3.0 cm En bloc resection NS NS: not speciﬁed; DF: disease free; PVNS: pigmented villonodular synovitis. reported that PVNS was well visualized on both proton density-weighted images and gradient-echo images despite the blurring eﬀect of hemosiderin-laden macrophages. The clinical diﬀerential diagnosis includes simple bursal cyst, neuroﬁbroma, ﬁbroma of tendon sheath, or a heman- gioma [1–11, 14]. A typical pes anserinus bursitis, meniscal, or ganglion cyst, may present with bursal ﬂuid and character- istic MRI signal. Chronic bursitis may present as solid mass and then other forms of synovitis and neoplasm need to be considered. Apart from having a typical clinical picture, rhe- umatoid synovitis will not show giant cells, foam cells, or his- tiocytes but will have abundant lymphocytes. Hemosiderotic synovitis, such as chronic trauma and hemophilia, may be radiologically indistinguishable. However, the surface and subsynovial tissues are much richer in hemosiderin- ﬁlled macrophages and typically lack the giant cells and