Local Recurrence of Invasive Micropapillary Breast Cancer After MammoSite Brachytherapy: A Case Report and Literature Review

Controversy exists over the optimal patient selection criteria for accelerated partial-breast irradiation (APBI), which has been introduced as an alternative to whole-breast irradiation. The goal is to select patients with the lowest risk for tumor spread outside of the original lumpectomy bed targeted by the local internal radiation dose. Therefore, patients with more aggressive types of breast cancer might not be ideal candidates for partial breast irradiation. We discuss the case of a 67-year-old woman who presented with local recurrence of invasive micropapillary breast cancer, a rare aggressive tumor type, 5 years after MammoSite brachytherapy. The patient's primary tumor possessed all favorable indicators except for the histology of invasive micropapillary carcinoma. This is the first report of invasive micropapillary carcinoma recurring after APBI. Although this is a single case, it supports the hypothesis that more aggressive types of breast cancer have a higher risk of local recurrence after APBI. We propose that invasive micropapillary carcinoma be considered a potential exclusion criterion until it can be validated in prospective clinical trials. More aggressive treatment approaches including whole-breast irradiation and/or chemotherapy might be needed to reduce the risk of local recurrence for invasive micropapillary breast cancer.