PT2N0M0 breast malignant adenomyoepithelioma: disease-free after excision and radiation

What happened, in summary

A 54-year-old woman had an abnormal screening mammogram showing a complex solid and cystic retroareolar lesion in the left breast. Targeted ultrasound confirmed a lobulated mass measuring 3.1 x 2.4 cm. Core biopsy initially suggested benign adenomyoepithelioma, with tumor cells showing p63 positivity, E-cadherin positivity, ER negativity, PR negativity, and HER2/neu negativity. She underwent wide local excision, and the first final pathology interpretation favored polymorphous low-grade adenocarcinoma with negative margins. Because of that diagnosis, she also had axillary nodal staging with sentinel lymph node biopsy, which was negative, and the disease was staged as pT2N0M0. Head and neck MRI found no separate primary tumor. After multidisciplinary review, she did not receive hormonal therapy or chemotherapy. She received adjuvant radiation to the whole left breast, 50.4 Gy, with a 10 Gy boost to the lumpectomy cavity, and tolerated treatment well. Several years later, the pathology slides were re-reviewed. The malignant component was found to be predominantly myoepithelial, p63-positive and CK7-negative, and the diagnosis was revised to malignant adenomyoepithelioma of the breast. After 78 months of follow-up, she remained alive with no evidence of disease. The reclassification changed the cancer story: the breast lesion was not a typical invasive ductal carcinoma and not simply the original low-grade adenocarcinoma diagnosis. The recorded treatment course remained local, with surgery and radiation only, because the sentinel node was negative and no systemic therapy was recommended at the time. This kept the final summary focused on local therapy and long-term disease control.