Atypical Hyperplasia of the Breast: The Black Hole of Routine Breast Cancer Screening

Aim: Determination of the prevalence, of the radiological and clinical characteristics, and outcome of atypical hyperplasia (AH) of the breast within a population subjected to routine screening (double-view mammography with double reading, performed every two years between 50 and 75 years of age). Patients and Methods: The clinical and radiological records and histological findings of percutaneous and surgical biopsy specimens of sixty-eight patients presenting with AH were reviewed together with patient follow-up data after percutaneous and surgical biopsy. Results: AH incidence in the population was 0.19‰ with the following distribution of lesions: atypical epithelial hyperplasia (AEH, 53%), columnar cell metaplasia with atypia (CCMA, 32%), and lobular intraepithelial neoplasia (LIN, 8%). The mean patient age was 58 years and 24% of patients were receiving hormone replacement therapy. The main radiological finding was the presence of microcalcifications for AEH and CCMA lesions in particular, and the mammograms were valid (correlation between American College of Radiology score and risk of lesion, only 3% of lesions were recognized on the second reading). A total of 13.7% of AH cases were underestimated and a real risk of AH progression was observed, regardless of whether or not surgical biopsy had been performed. Conclusion: The clinical and radiological characteristics of AH observed in a population subjected to routine breast cancer screening are identical to those for patients with the same lesions referred to specialist centers. Surgical biopsy remains the recommended option due to the risk of underestimation of lesions by percutaneous biopsy and the risk of progression justifies the need for continued close monitoring. Widespread routine screening for breast cancer combined with the development of imaging techniques (ultrasound, mammography and magnetic resonance imaging (MRI)) and percutaneous biopsies has increased diagnosis of atypical hyperplastic breast lesions. Accounting for just 3.6% of cases