Squamous Eccrine Ductal Carcinoma: A Comprehensive Review of the Clinicopathologic Features and Management in 27 Cases.

Squamoid eccrine ductal carcinoma (SEDC) is a rare cutaneous malignancy that demonstrates both squamous and eccrine differentiation. With a limited number of published cases in the literature, SEDC remains a diagnostic challenge. This retrospective chart review reports on 27 cases of SEDC identified at our institution and summarizes their clinical and histopathologic characteristics. Clinically, these tumors demonstrated a predilection for sun-exposed areas, favoring the head and neck (59.2%, n=16) of older individuals (median age 74 years). They presented as a papule, nodule, or plaque (48.1%, n=13) and were less than 2 cm in size. Despite surgical treatment with either conventional wide local excision or Mohs micrographic surgery, they had a local recurrence rate of 18.5% (n=5). One patient had metastatic disease with local recurrence, regional lymph node involvement, and distant skin metastasis, which led to the patient's death. Given that SEDC histologically exhibits both squamous and eccrine differentiation and immunophenotypically expresses markers of both eccrine/adnexal and squamous origin, this carcinoma poses a diagnostic challenge, as superficial biopsies may be indistinguishable from squamous cell carcinoma. This study emphasizes the importance of recognizing this tumor due to its recurrence risk and potential for metastasis and mortality.