Cutaneus metaplastic synovial CYST, a case report

The cutaneus metaplastic synovial cyst is a rare benign skin lesion,firstly described in 1987by Gonzalez et al. It is histologically characterized by a intradermal cystic cavity lined bymetaplastic synovial tissue that is often hyperplastic & protrude into it s lumen as villousstructure (with mesenchymal derivation, confirmed by immunohistochemical study).Mostreported cases have demonstrated a history of preceding trauma or post surgical cutaneusscar.The cutaneus metaplastic synovial cyst usually presents as a nondescript nodule with orwithout drainage ,so differential diagnosis include: suture granuloma, epidermal cyst, foreignbody granuloma, leiomyoma, eccrine poroma. Biopsy is necessary for making the correctdiagnosis. We report an 64-year old woman without a history of previous trauma or surgicalprocedure. The lesion is presented as a solitary tender subcutaneous nodule at right ankle.There have been only 24 cases reported in the English literature. so we decided to report thisrare case in Iran.