Incidence of cancer among patients with hidradenitis suppurativa.

BACKGROUND: On the basis of some case reports, a relationship has been suggested between hidradenitis suppurativa (HS) and the development of nonmelanoma skin cancer. OBJECTIVES: To confirm this relationship and to explore the risk of other cancers among patients with HS. PATIENTS: Patients with a discharge diagnosis of HS were obtained from the computerized database of hospital discharge diagnoses from January 1, 1965, through December 31, 1997. A total of 2119 patients with HS were identified. SETTING: All hospitals in Sweden. DESIGN: With record linkage to the Swedish National Cancer Registry, standardized incidence ratios (SIR [the ratio of the observed to expected incidence]) were calculated to estimate relative risk. RESULTS: The risk of developing any cancer in the cohort with HS increased 50% (95% confidence interval of SIR, 1.1-1.8, based on 73 observed cases). Statistically significant risk elevations were observed for nonmelanoma skin cancer (5 cases; SIR, 4.6; 95% confidence interval, 1.5-10.7), buccal cancer (5 cases; SIR, 5.5; 95% confidence interval, 1.8-12.9), and primary liver cancer (3 cases; SIR, 10.0; 95% confidence interval, 2.1-29.2). CONCLUSIONS: This study confirms an increased risk of nonmelanoma skin cancer among patients with HS. The risk for buccal cancer and primary liver cancer was also elevated among this cohort, but these associations should be interpreted cautiously because the combination of multiple significance testing and the few observed cases may have generated chance findings.