Infiltration of the pes anserinus complex by an extraarticular diffuse-type giant cell tumor (D-TGCT).

This report describes the case of a 26-year-old woman with a recurrent extraarticular diffuse-type tenosynovial giant cell tumor (D-TGCT) of the medial region of the knee affecting the pes anserinus and hamstring tendons. Presurgical MRI did not exclude infiltrative properties of the tumor. In the histological evaluation, the tumor showed an aggressive dispersion by infiltrating the collagenous tissue of the hamstring tendons. The treatment included a resection of the pes anserinus complex with distal semitendinosus and gracilis tendons. Regarding extraarticular D-TGCT a review of the literature showed a predominant affection of the medial region of the knee and thigh.