Background: Nonpuerperal mastitis may mimic breast cancer but the incidence of noninflammatory cancer among such patients is unknown.
Aim: To estimate the risk of breast cancer in patients with nonpuerperal mastitis within 12 months of treatment.
Study design: Two hundred seventy-seven patients with nonpuerperal breast inflammation were prospectively screened for breast cancer within 1 year after mastitis was diagnosed. The age-related standardized breast cancer incidence ratio of the female population was calculated.
Results: Five women (35, 43, 47, 61, and 72 years, respectively) were identified as having noninflammatory breast cancer independently, and at a location distant from the infectious lesion. In 1992, breast cancer incidence in the German federal state of Saarland was 110.0 new cases per 100,000 female inhabitants (0.11%). This gives a standardized incidence ratio in our study population of 37.8 (95% confidence interval: 12.3-88.1) i.e. 37 fold increase in risk.
Conclusion: Our data suggest that women with nonpuerperal mastitis (who do not have inflammatory breast cancer) are at significantly increased risk to have breast cancer diagnosed within 12 months following treatment. The reason for this higher incidence in the study population is unknown. Although benign mastitis is not thought to be a risk factor for breast cancer, patients warrant long-term surveillance after diagnosis.