Presentations

Abstract

Introduction: Endocrine mucin-producing sweat gland carcinoma (EMPSGC) is a rare cutaneous adnexal carcinoma that predominantly affects the eyelids and periorbital area, particularly in elderly women. Clinically, it typically presents as a painless, slow-growing, skin-colored nodule with relatively non-specific features. Histologically, EMPSGC is analogous to solid papillary carcinoma of the breast. It has been proposed that EMPSGC may serve as an in-situ precursor to primary cutaneous mucinous carcinoma (PCMC), also referred to as mucinous sweat gland adenocarcinoma with neuroendocrine features. In this case, we report on a 54-year-old male who presented with a painful, bleeding nodule on the left lateral zygomatic arch, persisting for 12 months.

Case Information: A 54-year-old male presented for evaluation of a painful, bleeding nodule on the left lateral zygomatic arch of 12 months' duration. He reported no prior treatment for the lesion and had no significant medical history. A shave biopsy was performed, and initial dermatopathological evaluation suggested a diagnosis of endocrine mucin-producing sweat gland carcinoma. The patient was referred for full excision via Mohs micrographic surgery. During the procedure, a second tumor was identified upon inspection of Stage 1. Both tumors were fully excised with clear margins, and the Stage 1 slides were sent for dermatopathological consultation. The consultation confirmed that the additional tumor was a mucinous sweat gland adenocarcinoma with neuroendocrine features, also known as primary cutaneous mucinous carcinoma (PCMC), occurring in association with the initially diagnosed EMPSGC. The patient recovered from surgery without complications and will continue to undergo regular skin examinations.

Discussion/Clinical Findings: EMPSGC is a rare but histologically distinctive cutaneous tumor that is typically indolent and non-metastatic. However, recent reports have described cases of EMPSGC with metastases, including to the salivary glands and, in one case, to the lungs. Although EMPSGC remains a very rare diagnosis, it has been hypothesized to represent an in-situ precursor to PCMC. The precise nature of the connection between EMPSGC and PCMC and whether EMPSGC directly precedes PCMC remains an area of ongoing investigation, though the association is now generally accepted. The findings of this case further support the notion that EMPSGC may indeed be a precursor lesion to invasive PCMC, highlighting the need for additional studies to further understand the molecular mechanisms underlying this progression.

Conclusion: This case involved a patient who underwent Mohs micrographic surgery for a biopsy-proven endocrine mucin-producing sweat gland carcinoma on the left lateral zygomatic arch. Upon excision and examination via Mohs surgery, a concurrent diagnosis of primary cutaneous mucinous carcinoma was made. Both entities are extremely rare and presented in an unusual location in this case. Moreover, the occurrence of PCMC in association with EMPSGC as seen in this case gives further reinforces the concept, though still debated but increasingly accepted, that EMPSGC exists on a spectrum as a precursor to invasive PCMC, both of which may be less indolent than previously thought.