Low-Grade Sweat Gland Carcinomas: A Review-A CME Article.

BACKGROUND

Primary cutaneous adnexal carcinomas (PCACs) are rare and biologically heterogeneous neoplasms that present significant diagnostic and therapeutic challenges. Among them, microcystic adnexal carcinoma (MAC), syringoid eccrine carcinoma (SEC), primary cutaneous adenoid cystic carcinoma (PCACC), secretory carcinoma, apocrine cribriform carcinoma (PCCAC), primary cutaneous mucinous carcinoma, and neuro-endocrine mucin-producing sweat gland carcinoma are clinically and histologically distinctive yet frequently confused with one another.

OBJECTIVE

To synthesize and critically appraise current evidence on the clinicopathological, immunophenotypic, and molecular hallmarks of the 7 PCAC entities and to translate this knowledge into practical diagnostic and management guidance for dermatopathologists and oncologists.

METHODS

A narrative review of the English-language literature was conducted using PubMed/MEDLINE without date restriction. Search terms combined tumor-specific headings with keywords for epidemiology, histology, immunohistochemistry, molecular genetics, and management. Eligible articles included original studies, systematic reviews, and relevant case series describing MAC, SEC, PCACC, secretory carcinoma, PCCAC, endocrine mucin-producing sweat-gland carcinoma, or primary cutaneous mucinous carcinoma.

RESULTS

Distinct architectural patterns together with a focused immunohistochemical panel (eg, Ber-EP4-/EMA+ in MAC, K77+ in SEC, CD117/MYB+ in PCACC, pan-TRK+ in secretory carcinoma) and key molecular signatures (TP53/JAK1, MYB-NFIB, ETV6-NTRK3) reliably discriminate the 7 major low-grade sweat gland carcinomas. These insights translate directly into management, guiding Mohs surgery for the infiltrative, nerve-tracking tumors and enabling tropomyosin receptor kinase inhibitor therapy for advanced secretory carcinoma.

CONCLUSIONS

Accurate recognition of PCACs requires integrative interpretation of morphology, immunoprofiles, and molecular findings supported by deep, full-thickness biopsy. Awareness of entity-specific patterns reduces misdiagnosis, guides appropriate surgical margins, and informs the selective use of ancillary testing and targeted therapies.