Interpretation of the risk associated with the unexpected finding of lobular carcinoma in situ

Background: The risk of developing invasive breast cancer after finding lobular carcinoma in situ (LCIS) is controversially reported in the literature. The surgeon who finds LCIS unexpectedly may be tempted to remove the breast, or even remove both breasts. Methods: From 1976 to 1991, 157 consecutive women with palpable or mammographically detected breast lesions underwent surgery to resolve doubt as to the presence of invasive cancer. We report on the women in whom LCIS was found after diagnostic breast surgery and analyze the incidence of breast cancer after a mean 5 years of follow-up in comparison with that in the normal reference population. Results: Eight patients developed infiltrating breast carcinoma (four ipsilateral, four contralateral as first events), equal to a homolateral rate of 0.00625. The expected rate in the normal reference population is 0.00152; ratio 4.11 (95% confidence interval 1.1-10.5). For a contralateral event the rate ratio is 3.0 (95% confidence interval 0.8-7.6). Conclusion: LCIS is one of many markers for later infiltrating cancer, so patients should be carefully followed. Ablative surgery is not justified.