Primary cutaneous adenoid cystic carcinoma in the United States: Incidence, survival, and associated cancers, 1976 to 2005

BackgroundPrimary cutaneous adenoid cystic carcinoma (PCACC) is a rare appendageal tumor of uncertain origin. Details on epidemiologic features of PCACC are sparse and largely based on clinical reports.ObjectiveWe sought to develop an understanding of PCACC incidence, survival, and associated cancers using population-based data.MethodsWe used the Surveillance, Epidemiology, and End Results program to calculate age-adjusted incidence rates (IRs), IR ratios, 95% confidence intervals, standardized incidence ratios (SIRs), and 5-year relative survival of PCACC diagnosed during 1976 to 2005.ResultsIn a population of 723,174,580 person-years, the overall PCACC IR was 0.23 per 1 million person-years (n = 152), with similar IRs among male and female patients (IR = 0.24). Most cases of PCACC presented at a localized stage and arose on the face/head/neck. Among 122 of the 2-month survivors of PCACC and more than 2.4 million 2-month cancer survivors, risk of associated cancers overall was not significantly increased (SIR = 1.17 [n = 24] and SIR = 1.43 [n = 16], respectively). However, PCACC was associated with significantly increased risks of subsequent lymphohematopoietic (n = 6; SIR = 3.70) and thyroid (n = 2; SIR = 15.25) cancers, whereas the converse associations were not observed. Five-year relative survival was excellent (96.1%; n = 122) with more favorable survival noted for PCACC involving the face/head/neck than the trunk.LimitationsA pathologic review of reported cases was not undertaken.ConclusionPCACC is a rare appendageal tumor that affects male and female individuals equally, primarily presents at localized stage, predominates in the face/head/neck, and is associated with favorable survival. Immunosuppression does not appear to contribute to the development of PCACC, and the observed associated cancer patterns will need to be confirmed in larger studies.