Abstract:

Primary cutaneous mucinous carcinoma and its precursor, endocrine mucin-producing sweat gland carcinoma are two exceedingly rare low-grade malignant tumors of probably eccrine or apocrine origin. They are slow-growing tumors with a predilection for the eyelid and periorbital skin of middle-age to elderly females. The histopathology archives from our institution yielded seven cases of mucin-producing carcinomas of the skin that were diagnosed during the last 20 years. The patients mean age at diagnosis was 65 years (range 53-78 years). Most (71%) of the patients are females. All the lesions occurred in the eyelids region. Most of the cases were diagnosed on an excisional biopsy then a completion excision was done as needed. Based on our records, only one case showed multiple recurrences. Microscopically, two cases showed pure mucinous carcinoma with nests of monomorphic low-grade cells floating in mucin pools with no associated in situ component. Two more cases showed a combination of mucinous carcinoma and solid nests of tumor cells lacking myoepithelial cell layer. The last three cases revealed similar morphology but with an associated in situ component, highlighted by myoepithelial cells cocktail, and including a case of endocrine mucin-producing sweat gland carcinoma with a predominant in situ component looking like ductal carcinoma in situ. We applied immunohistochemical (IHC) stains, including estrogen receptor (ER), low molecular weight cytokeratin (Cam 5.2) with myoepithelial cells cocktail (MEC) and Synaptophysin, on representative sections from all the cases. IHC stains were contributory in six cases. Strong and diffuse expression of ER and Cam 5.2 and at least focal expression of Synaptophysin was observed in all of the cases. Our limited case series study highlights the utility of basic immunohistochemical stains in the diagnosis of primary mucinous carcinoma of the skin, its precursor and in situ components.

Financial Disclosure:
No current or relevant financial relationships exist.

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Zainab Harb, MD