Occult Histopathology and Its Predictors in Contralateral and Bilateral Prophylactic Mastectomies.

Background: The last decade has seen an increasing prevalence of prophylactic mastectomies with decreasing age of patients treated for breast cancer. Data are limited on the prevalence of histopathologic abnormalities in this population. This study aimed to measure the prevalence of histopathologic findings in contralateral prophylactic mastectomy (CPM) and bilateral prophylactic mastectomy (BPM) patients and identify predictors of findings.

Methods: Our institution's prophylactic mastectomies from 2004 to 2011 were reviewed. Breast specimens with prior malignancies were excluded. Patient factors and pathology reports were collected. Independent predictive factors were identified with univariate and multivariate logistic analysis.

Results: A total of 524 specimens in 454 patients were identified. Malignancy was found in 7.0% of CPM and 5.7% of BPM specimens. In CPM patients, ipsilateral lobular carcinoma-in situ [odds ratio (OR) 4.0] and mammogram risk group (OR 2.0) were predictive of malignancy. Age group (OR 1.5), ipsilateral lobular carcinoma-in situ (OR 2.3), and prior bilateral salpingo-oophorectomy (OR 0.3) were predictive of moderate- to high-risk histopathology. Only increasing age group was predictive of increased moderate- to high-risk histopathology in BPM patients (OR 2.3). There were no independent predictors of malignancy in BPM. BRCA status was not predictive in either CPM or BPM.

Conclusions: Patients with lobular carcinoma-in situ in the index breast or high-risk mammograms have a higher prevalence of malignancies. Although BRCA patients may benefit from prophylactic mastectomy, the genetic diagnosis does not increase the prevalence of detecting occult pathology. BPM patients can be counseled about relative risk, where occult pathology increases with age.