Pigmented villonodular bursitis/diffuse giant cell tumor of the pes anserine bursa: a report of two cases and review of literature.

Pigmented villonodular synovitis (PVNS) is a benign but potentially aggressive lesion, characterized by synovial villonodular proliferation with hemosiderin pigmentation and stromal infiltration of histiocytes and giant cells. This consists of a common family of lesions, including localized and diffuse forms of pigmented villonodular synovitis, giant cell tumor of the tendon sheath (nodular tenosynovitis) and the very rare cases of extra-articular pigmented villonodular synovitis arising from the bursa (pigmented villonodular bursitis or diffuse giant cell tumor of the tendon sheath). The purpose of this paper is to present two rare cases of pigmented villonodular bursitis arising from the pes anserinus bursa. The various differentials along with a review of literature of similar lesions are also being discussed. However, as with other lesions, clinicoradiographic features along with close histological correlation is essential for diagnosis.