Merkel Cell Carcinoma In Situ Arising in a Trichilemmal Cyst: A Case Report and Literature Review

Abstract

A 73-year-old man presented with a 4-mm asymptomatic, smooth, dome-shaped lesion on the right fourth finger with a clinical impression of a cyst/dermatofibroma. Histological examination showed a trichilemmal cyst with 3 nests of small blue round cells within the basal layer of the cyst lining. There were many mitotic figures and apoptotic bodies. The stain for cytokeratin 20 "decorated" the tumor cells with an unequivocal perinuclear dot-like pattern, confirming their Merkel cell origin. Dermal Merkel cell carcinoma (MCC) arising in association with benign adnexal tumors or cysts, with or without epithelial involvement, is a rare event. MCC in situ in this context has not been previously reported. The immunostain for cytokeratin 20 is an important ancillary study in diagnosing MCC. Our case supports the view that a subset of MCCs is of intraepithelial origin and underscores the clinical importance of surveillance for changes in an "innocent" cyst.

Incidence and clinical significance of lesions presenting as a scalp mass in adult patients

“…In this subtype, gradual enlargement and locally aggressive behavior with recurrences and seldom with metastases can be seen [11]. Although we could not define any association, some carcinomas, e.g., Merkel cell carcinoma, were correlated to trichilemmal cysts [7]. With respect to our series, the proliferating subtype was seen in 3.5 % (5/140) of the trichilemmal cysts.…”

“…The informed consent of each and every patient was obtained before the procedures. The patient charts were retrospectively investigated for (1) surgery departments and repeated surgeries, (2) demographic features, (3) pathology reports, (4) surgical notes and number of surgeries, (5) preoperative and postoperative diagnosis, (6) laterality and location of the lesions, if noted, (7) radiological studies and (8) further managements.…”

Trichilemmal Cyst With Carcinoma In Situ Within an Atypical Fibroxanthoma

“…17,18 Merkel cell carcinoma has been reported in keratinous skin cysts including epidermal 19 and trichilemmal cysts. [20][21][22] But there has been no report of severe dysplasia/ carcinoma in situ within a trichilemmal cyst in the literature. The other trichilemmal proliferations include proliferating trichilemmal cyst (pilar tumor) and its malignant counterpart.…”

Evolving Paradigm in Treatment of Merkel Cell Carcinoma of the Digit from Ray Resection to Wide Local Excision and Flap Coverage

“…Blue dye was used to find the sentinel lymph nodes nodes were negative. Six years later, there has been no recurrence [16].…”

“…Even though the Surveillance, Epidemiology, and End Result (SEER) database reported 1234 (24 %) Merkel cell carcinomas in the hand and upper extremity from 1986 to 2009 [5], there are only 11 case reports of MCC of the digit found in PubMed, Medline, and MD Consult databases [6][7][8][9][10][11][12][13][14][15][16]. Although over a thousand cases were identified in the SEER database, there was no further subdivision of the upper extremity.…”