Mucinous Syringometaplasia: Practical Insights from a New Case.

Mucinous syringometaplasia is a rare adnexal process that may mimic mucinous carcinoma or metastatic mucinous adenocarcinoma, creating diagnostic challenges. After reviewing the recent report by Furtado et al, we present a brief additional case involving a longstanding ulcerated plaque on the dorsal hand of a 61-year-old man. Histology demonstrated an epidermal invagination connected to eccrine ducts lined by nonkeratinizing squamous epithelium with abundant goblet cells, strongly positive with Alcian blue, and negative for CDX2, supporting a primary cutaneous eccrine-derived mucinous metaplasia. We emphasize 2 practical considerations: the limited sensitivity and specificity of CDX2 in excluding gastrointestinal primaries, and the importance of correlating morphology with mucin stains and a focused immunohistochemical panel to avoid overdiagnosis. We further note that mucinous syringometaplasia is likely a reactive/metaplastic phenomenon related to local irritation or trauma, and encourage standardized diagnostic criteria and multicenter registries to improve understanding of its incidence, behavior, and diagnostic pitfalls.