Cutaneous Metaplastic Synovial Cyst: A Case Report and Literature Review

Cutaneous metaplastic synovial cyst (CMSC) is a rare cutaneous lesion characterized by a tender subcutaneous nodule, which usually occurs at the site of previous surgical or local trauma. Histologically, the lesion includes a cystic structure with villous-like projections and a lining mimicking hyperplastic synovium.

We reported the first case of CMSC which developed at the surgical incision site of treatment of a maxillofacial fracture. In addition, we reviewed English literature to evaluate all previously reported CMSC cases and discussed its clinical and histopathological features and etiology. From 1987 to now, reviewing the English literature about CMSC includes 17 studies that described 28 cases, and our presented case was the 29th. There was no sex predilection and age of patients ranged from 7 to 82 years, but most of them were over 40 years. We can see this lesion in any site of the body and hand/arm is the most prevalent involved region (28% cases). Most of the patients had a history of previous local trauma or operation in the involved area.

Although the actual etiology of CMSC remains unclear, trauma, as the most probable etiologic factor, plays a role in development of CMSC. Surgical excision of the lesion is the preferable treatment choice and rate of recurrence is low.