Carcinoma arising within fibroadenomas of the breast. A clinicopathologic study of 105 patients.

The authors report the clinicopathologic features of 105 carcinomas arising within fibroadenomas (FAs) of the breast. The mean age of the patients was 44 years. The presentation and gross characteristics of these tumors rarely differed from those of uncomplicated FAs. Carcinoma in situ (CIS) was the predominant type of malignancy (95%) found to arise in FAs, and lobular and ductal types occurred with equal frequency. Nine of ten FAs harboring an invasive carcinoma also contained CIS supporting the origin of the infiltrative component in the FAs. CIS within FAs was associated with in situ malignancy in surrounding breast tissue in 21% of cases. Age, fibroadenoma size, and type and extent of CIS were similar in patients with disease limited to the FA and in those with associated malignant disease in the remainder of the breast. Axillary nodal metastases were not detected. Sixty-three patients were observed for a mean period of 8.4 years. Only one of 26 patients with CIS within an FA who was treated conservatively developed an ipsilateral carcinoma. None of the 26 developed contralateral carcinoma; however, 3 of 23 with similar lesions, who were treated by mastectomy, did so. The contralateral carcinomas were invasive in two patients, one of whom died with distant metastases. Seven patients with FAs harboring lobular CIS underwent bilateral mastectomy. Their postoperative course was uneventful. None of seven patients with invasive carcinoma arising in an FA, two of whom were treated conservatively, succumbed to disease. However, one developed contralateral carcinoma. The authors recommend breast-conserving therapy for CIS arising in an FA.