Surgical management and lymph-node biopsy of rare malignant cutaneous adnexal carcinomas: a population-based analysis of 7591 patients

Objective: To analyze the prognosis of cutaneous adnexal malignancies, survival relative to surgical management, and utility of lymph-node biopsy. Design: Population-based study of the SEER-18 database from 1975 to 2016. Participants: 7591 patients with sweat gland carcinoma, hidradenocarcinoma, spiradenocarcinoma, sclerosing sweat duct tumor/microcystic adnexal tumor (SSDT/MAC), porocarcinoma, eccrine adenocarcinoma, and sebaceous carcinoma Results: Five-year OS ranged from 68.0 to 82.6%, while 5-year DSS ranged from 94.6 to 99.0%. The majority of patients were treated with narrow (42.4%) or wide local excision (16.9%). DSS at 5 years showed that patients with stage IV had significantly poorer survival (50.3%) than I, II, or III (99.3%, 97.8%, and 89.0% respectively). 5-year OS was significantly higher for narrow excision (excision with < 1 cm margin, 78.5%) than observation (65.0%), excisional biopsy (66.8%), or wide local excision (WLE, 73.2%). Lymph-node biopsy was performed in a minority of cases (8.1%) and patients showed no significant difference in survival based on nodal status. The sensitivity and specificity of lymph-node biopsy for all malignancies were 46% and 80%, respectively. The PPV and NPV for that group were 0.46 and 0.80, respectively. Invasion of deep extradermal structures was a poor predictor of nodal positivity. Conclusions: These malignancies have excellent DSS. Narrow excisions demonstrate better 5-year DSS and OS compared with WLE. Lymph-node biopsy is a poor predictor of survival in advanced stage disease and utility is limited.