A case of fibroadenoma with lobular carcinoma in situ and microinvasion in a young woman

Fibroadenomas are benign breast tumors with a rare incidence of malignant transformation. Carcinoma arising within fibroadenomas typically occurs in women above the age of 40. We present a case of a young patient with microinvasive carcinoma arising within a biopsy-proven fibroadenoma, highlighting the possibility of carcinoma arising within fibroadenomas in young patients and the importance of vigilant surveillance even after a benign biopsy. In younger patients, new suspicious changes in benign lesions should be investigated. If prior core needle biopsy was performed, excision biopsy should be considered as the malignancy may be small and may be missed on needle biopsy.