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

Abstract

Cutaneous metaplastic synovial cysts (CMSCs) are rare tumors typically comprising a solitary, wellcircumscribed cystic mass that is not connected to the joint. Synovial cysts have been reported predominantly by orthopedists or pathologists; however, the presence of CMSC is not generally well recognized by dermatologists. Herein, we report a CMSC in a 68-year-old woman receiving systemic corticosteroid therapy for the treatment of eosinophilic granulomatosis with polyangiitis (EGPA). We attempt to delineate the clinical characteristics of this unusual neoplasm by reviewing the literature, focusing especially on dermatological descriptions. Histologic examination of the surgical specimen in the current case revealed that the cystic wall was lined with layers of flattened synovial cell-like cells and connective tissues, mimicking the synovial membrane. Positive immunoreactivity of the lining cells against vimentin was detected, but no immunoreactivity against cytokeratin, carcinoembryonic antigen (CEA), CD68, or S-100 was detected. The pathogenesis of CMSC remains unclear, but it has been tightly linked to direct traumatic stimuli or relative tissue fragility, which potentially accounts for CMSC development in our case. Most CMSCs reported by dermatologists are located on the extremities, whereas those described by other specialists tend to be distributed more globally. Preoperative diagnoses are often either epidermal cyst or suture/foreign body granuloma. Incomplete surgical excision of usual synovial cysts may lead to local recurrence, which has been reported in oral and maxillofacial surgery, but not in dermatologic surgery. This fact could be explained by the technical difficulties of surgical excision related to anatomical location. Dermatologists need to be aware of CMSC, and CMSC should be included in the differential diagnosis of subcutaneous cysts.

Unprecedented recurrence of carpal tunnel syndrome by metaplastic synovial cyst in the carpal tunnel

“…Trauma is the most common etiology for MSC. In the review of literature performed by Fukuyama declared that just 30 cases have been reported in the literature and 17 cases of MSC (59%) developed at the scar site of operations or trauma 17 . Our case is the 18th case in literature reported after trauma.…”

“…This can be explained by the technical difficulties of surgical excision associated with anatomic location. Close follow-up may be recommended for patients with a risk of recurrence like repetitive surgery, trauma or underlying diseases that predispose to the development of MSC 17 . The recommended method of MSC treatment is excision 18 .…”

Painless Mobile Nodule on the Shoulder

“…2 Clinically, the lesion typically presents as a solitary subcutaneous nodule that may be tender or painless. In a literature review of CMSC cases performed by Fukuyama et al, 3 distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature, [3][4][5][6][7][8][9] including our present case.…”

“…In a literature review of CMSC cases performed by Fukuyama et al, 3 distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature, [3][4][5][6][7][8][9] including our present case. The pathogenesis remains uncertain; however, a majority of previously reported cases of CMSC characteristically have been associated with a pre-existing lesion, with most presentations developing at surgical scar sites secondary to operation or trauma.…”