Atypical ductal hyperplasia and carcinoma in breast fibroadenoma:a clinicopathological analysis of six cases

CHEN Chen; XIE Xiaoli; PAN Yulin; LI Guoxia

doi:10.3969/j.issn.1007-8096.2026.01.005

Abstract：Objective To investigate the clinicopathological features of atypical ductal hyperplasia and carcinoma transformation in breast fibroadenoma(FA).Methods A retrospective analysis was conducted on clinical and pathological data from 2012 to 2024,encompassing HE staining,immunohistochemical examination,and literature review.Results Among 3,975 patients with FA,3 cases developed atypical hyperplasia and 3 cases progressed to carcinoma,with an incidence rate of 0.15%(6/3,975).One case was an invasive carcinoma within a FA.All patients were female,aged between 19 and 71 years.Grossly,the tumors appeared as grayish-white nodules with well-defined margins,measuring 1.2 to 4.5 centimeters in diameter,having a solid texture,and a firm or hard consistency,with fissure-like patterns.Microscopically,there was ductal hyperplasia with epithelial and myoepithelial linings,and a loose connective tissue stroma.Atypical hyperplasia and ductal carcinoma in situ exhibited hyperplastic ductal epithelium with uniform cells but atypia,creating a sieve-like appearance.Invasive carcinoma showed nests of highly atypical cells infiltrating the surrounding tissue,accompanied by calcification,ossification,and fibrosis.The immunophenotype was as follows:CK5/6 was negative,and ER was positive in atypical hyperplasia and ductal carcinoma in situ(DCIS);ER,PR were negative,HER2 was strongly positive(3+),and CK5/6 was negative in invasive carcinoma.Imaging revealed that atypical hyperplasia and DCIS masses had regular morphology with well-defined borders,a BI-RADS-3 grade similar to benign FA,whereas invasive carcinoma exhibited a BI-RADS-4 grade comparable to malignant tumors,differing primarily in margin definition.Postoperative follow-up ranged from 4 to 57 months,with no recurrence or metastasis observed.Conclusion Malignant transformation of fibroadenoma is rare,while atypical hyperplasia and ductal carcinoma in situ are relatively more common compared to invasive carcinoma.After surgical resection,endocrine therapy or chemotherapy is administered,with follow-up ranging from 1 to 5 years,during which all patients exhibit favorable prognosis.The atypical hyperplasia and DCIS within fibroadenomas appear macroscopically and on ultrasound similarly to benign fibroadenomas,potentially leading to oversight.Therefore,even fibroadenomas warrant follow-up.Performing a biopsy or mass excision serves as an effective diagnostic and therapeutic approach.