Introduction/Background Fibroadenoma is the most common benign breast neoplasm seen in young women under 30 years of age.Cancer within fibroadenoma is usually found incidentally during pathologic examination, with reported incidences ranging from 0.002% to 0.125%.

Methodology We retrospectively report seven cases of carcinomas arising in mammary fibroadenomas to report clinical, radiological and histological characteristics of breast carcinoma arising within fibroadenoma.

Results The average age of patients was 41 years (26–53) with a mean delay of consultation of 92 days (15–365 days). In three cases, fibroadenomas were complex, containing cysts, adenosis and apocrine metaplasia. Carcinomatous lesions were dominated by the invasive type. Invasive ductal carcinoma was found in four cases, associated in one case with ductal carcinoma in situ (DCIS) and with mucinous colloid carcinoma in the other one. Lobular invasive carcinoma associated with lobular carcinoma in situ in one case (LCIS). In the two other cases, a focus of LCIS and DCIS was found arising from a complex background of fibroadenomas. Fibrocystic dystrophy lesions were found in the adjacent parenchyma associated in one case to intralobular neoplasia lesions. The treatment consisted of a lumpectomy in one case, conservative treatment in three cases and a mastectomy associated to axillary node dissection in the three others. Radiotherapy was indicated in six cases and chemotherapy done in four cases. After a mean follow up of 3, 57 years (1–7) no sign of recurrence was reported.

Conclusion Although malignant changes are rare, the risk of malignancy inside a fibroadenoma should be kept in mind. Thus, follow-up is advised, and biopsy or excision is needed if any progressive changes or increase in size is seen.