Periocular Endocrine Mucin-Producing Sweat Gland Carcinoma and Mucinous Carcinoma—An Institutional Series Including 49 Patients

Endocrine mucin-producing sweat gland carcinomas (EMPSGCs) are rare adnexal tumors with a predilection for the periocular region, which can progress to primary mucinous carcinoma (MC). Understanding of the clinical and histopathologic features of these carcinomas is still evolving. We present a single-institution series of 45 EMPSGC in 38 patients, and 20 MC in 11 patients arising in the eyelids and periocular region. EMPSGC and MC patients had similar mean ages at presentation (67 and 58), and both were more common in women. One EMPSGC involved bilateral eyelids at presentation, and both tumor types recurred in some cases, but no extensive invasion or metastatic disease was identified. In five MC patients, microscopic examination identified EMPSGC precursor regions within the lesion, while these were absent in the remaining six. Immunohistochemical markers of neuroendocrine differentiation varied over the study period, with INSM1 and synaptophysin used most frequently. INSM1 showed stronger and/or more extensive immunoreactivity in most, but not all, cases. All five patients with EMPSGC-associated MC had tumors positive for a neuroendocrine marker. Finally, all three of the tested EMPSGCs expressed MYB based on RNA in situ hybridization. Our findings support the female predominance in these tumors and their potential for multicentric or bilateral disease at presentation, as well as the capacity of EMPSGC to progress to MC.