Breast carcinoma arising in a fibroadenoma: A case series of 16 patients and review of the literature.

Breast carcinoma arising from a fibroadenoma is an uncommon entity and is frequently detected incidentally during pathological examination or excisional biopsy of a benign breast tumor. Due to only sporadic cases being reported, evidence-based guidelines are not well-established to date. The present report describes 16 patients diagnosed with breast carcinoma arising within a fibroadenoma in the Third Hospital of Nanchang (Nanchang, China) between January 2019 and December 2021 and discusses the clinicopathological characteristics, imaging findings and treatment. The age of patients at diagnosis ranged between 19 and 58 years and a well-defined asymptomatic mass was the most common clinical presentation. Carcinoma occurring in fibroadenoma generally mimics a benign tumor and potential carcinomatous changes may not be detected. Pathologically, carcinoma was the predominant subtype in the present study. Additionally, ductal carcinoma was more common compared with lobular carcinoma in the present case series. Regarding the molecular phenotypes, the majority of cases were categorized as luminal subtype, although other subtypes such as triple-negative and HER2 positive breast cancer were also identified. In the present study, seven patients were treated with breast-conserving surgery and nine patients were treated with mastectomy. Sentinel lymph node biopsy was performed in all patients and none exhibited axillary node metastasis. Additionally, six patients underwent radiotherapy and two received chemotherapy. During the follow-up, all patients were alive and no evidence of disease relapse was observed. In summary, clinicians should be aware of the possibility of carcinoma within a fibroadenoma, which could alter the therapeutical course. Adequate biopsy or excision should be performed in patients with indicators of malignant transformation in a presumed benign breast tumor.