Multicentric endocrine mucin‐producing sweat gland carcinoma and mucinous carcinoma of the skin: A case report

Endocrine mucin‐producing sweat gland carcinoma (EMPSGC) is a rare low‐grade sweat gland carcinoma. EMPSGC is thought to be a precursor to mucinous carcinoma of the skin (MCS). Since the first description of EMPSGC in 1997, only a few cases have been reported, and its etiology and mechanisms remain unknown. In this report, we describe a 71‐year‐old Japanese woman with two isolated EMPSGC and one MCS lesion on her face. She was simultaneously diagnosed with invasive ductal carcinoma of the breast. She had a history of uterine cancer of unknown histopathological diagnosis 24 years previously. The presence of in situ lesions confirmed by myoepithelial cells suggested that the cutaneous lesions were primary tumors. To the best of our knowledge, this is the first case of multiple primary EMPSGC/MCS tumors. Additionally, this might be the first case with multiple primary carcinomas including adnexal cutaneous tumors, breast cancer, and uterine cancer, which may share the common feature of expressing female hormonal receptors. This case indicates that EMPSGC/MCS may be triggered by a hormonal receptor abnormality, perhaps because of genetic defects. A larger number of reports examining this issue may be necessary to further assess our initial observations.