Cutaneous Metaplastic Synovial Cyst of the First Metatarsal Head Area

Abstract

A cutaneous metaplastic synovial cyst (CMSC) is a cyst lined with metaplastic synovial tissue, which includes the formation of an intracystic villous structure resembling hyperplastic synovial villi. Clinically, the lesion is a tender, subcutaneous nodule that usually occurs at the site of previous surgical trauma and is frequently misdiagnosed as a suture granuloma. The actual cause remains unclear; however, trauma is presumed to be a precipitating factor, as most reported cases have demonstrated a history of antecedent cutaneous injury. Here, we present a case of CMSC in a 51-year-old woman who presented with a cystic mass localized in the left sole. She had no history of previous trauma or surgical procedures performed in the area. Although the case explained in this report is a spontaneous case of CMSC that occurred without a history of trauma, it is believed to have been caused by constant and chronic pressure since CMSC occurred in the first metatarsal head area, a part of the sole where heavy pressure is consistently applied.

Cutaneous Metaplastic Synovial Cyst

“…When located close to a joint cavity, these lesions need to be differentiated from the fluid-filled sacs of bursitis, which are deeper in the subcutaneous tissue and located over the bony prominences. 1 IHC testing in CMSC cases shows positive staining for vimentin and negative staining for the S100 protein, carcinoembryonic antigen and CD34. CD68 shows a variable reaction.…”

“…Also known as synovial metaplasia of the skin, CMSC is a rare cystic tumour first described in 1987 by Gonzalez et al 1 The tumour is located intradermally or subcutaneously and is lined by a hyperplastic synovium-like membrane associated with transepidermal fistulae. 2 The aetiology remains unknown, although a history of trauma or surgery is noted in most cases, suggesting that surgical or composed of hypo-and hypercellular areas with a mixture of fibroblasts, epithelioid cells, mononuclear inflammatory cells and occasional multinucleated giant cells.…”

“…2 The aetiology remains unknown, although a history of trauma or surgery is noted in most cases, suggesting that surgical or composed of hypo-and hypercellular areas with a mixture of fibroblasts, epithelioid cells, mononuclear inflammatory cells and occasional multinucleated giant cells. 1,3 Hypocellular areas show fibrin deposits and hyalinisation. When located close to a joint cavity, these lesions need to be differentiated from the fluid-filled sacs of bursitis, which are deeper in the subcutaneous tissue and located over the bony prominences.…”

Cutaneous Metaplastic Synovial Cyst: Case Report and Literature Review from the Dermatological Point of View

“…1 Histologically, the cystic cavity is surrounded by synovial celllike cells that resemble the cells observed in hyperplastic synovium. 2 Villous-like structures often protrude into the lumen of the cyst. 2 CMSC usually appears at the site of previous surgery or trauma and is not related to joint or synovial structures.…”

“…2 Villous-like structures often protrude into the lumen of the cyst. 2 CMSC usually appears at the site of previous surgery or trauma and is not related to joint or synovial structures. 3 CMSC is not considered to be a true cyst because it lacks a definite epithelial lining.…”