Cellular fibroepithelial lesions of the breast: A long term follow up study

Some fibroepithelial lesions (FEL) of the breast are difficult to classify as cellular fibroadenoma (CFA) or benign phyllodes tumor (BPT) due to overlapping histologic features. This indeterminate group is histologically characterized by prominent stromal cellularity, mild atypia, and mitotic activity. The local recurrence potential of cellular FEL (CFEL) has been insufficiently studied. The objective of this study was to evaluate the histologic features, characterize the long-term follow-up and recurrence rate of CFEL, and compare this data with the recurrence rate of definitive BPT. Ninety CFEL that were <4 cm were recovered from the benign breast disease cohort. The control group comprised of 10 randomly selected patients with BPT. Cases were classified based on a combination of mitotic activity, intracanalicular growth, stromal atypia, stromal prominence, and fat infiltration. None of the CFEL was widely excised. Of the 90 CFEL cases, there were 22 BPT-like, 35 CFA, and 33 indeterminate. The mean age of the patients was 40.1 years. The mean tumor size was 2.4 cm. All patients had at least two years of follow-up (median 27). None of the patients with BPT-like CFEL showed ipsilateral recurrence. Five of the 35 patients with CFA had recurrent ipsilateral CFA. This occurred within 1 to 11 years after the initial diagnosis. One of 33 patients with indeterminate type had a recurrent ipsilateral lesion five years after the initial diagnosis with histologic features of CFA. None of the patients in control group had any recurrence. In conclusion, as a group, CFEL have a low proclivity for recurrence, even when enucleated with close or positive margins. The presence of histologic features of BPT did not correlate with an increased potential for recurrence.