Evaluating the Significance of Atypical and Malignant Breast Lesions Arising in Fibroadenoma of the Breast

Context While fibroadenomas (FAs) are the most common benign neoplasm of the breast, little data exists about the clinical characteristics and prognostic value of FAs found to be directly associated with atypical and malignant lesions. Objective Cases of FA of the breast were reviewed to establish the exact clinical significance of these lesions involved by atypia and malignancy. Design All FA cases diagnosed on core needle biopsy (CNB) between 2013 and 2022 were screened to identify atypical and malignant lesions {(atypical lobular hyperplasia (ALH), lobular carcinoma in situ (LCIS), atypical ductal hyperplasia (ADH), flat epithelial atypia (FEA), ductal carcinoma in situ (DCIS), invasive ductal carcinoma (IDC), and invasive lobular carcinoma (ILC)} arising in FA. The relationship between CNB and excisional findings for each case was reviewed. Results A total of 1500 cases of FA diagnosed on CNB were identified. Among these, 23 cases showed atypical and/or malignant lesions within FA. The median age at diagnosis was 53 years. Of those 23 cases, five were LCIS, one was LCIS+ILC, one was LCIS+ALH, one DCIS+IDC, one was LCIS+DCIS, three were ADH, seven were ALH, and four were DCIS. For LCIS, the excision showed LCIS (2/5), LCIS + ALH (1/5), LCIS + DCIS (1/5), LCIS + DCIS + ALH (1/5). For DCIS, excisions showed Invasive carcinoma with mixed ductal and lobular features (1/4), LCIS + DCIS (1/4), LCIS + DCIS + IDC [classic and pleomorphic type] (1/4), no residual carcinoma (1/4). For ALH, excision showed ALH (2/7), no residual ALH (2/7), ALH+IDP (Intraductal Papilloma) (2/7), LCIS (1/7). For ADH, DCIS (1/3), and benign findings (2/3). For LCIS+ILC and DCIS+IDC, the excisional findings were the same. For LCIS+ ALH, the excisional findings showed benign findings with the radial scar (1/1). Conclusion There is a low percentage of FA harboring atypia or carcinoma. Due to the high upgrade rate following excision, complete excision of these lesions may guide recommended method of clinical management