Breast adenomyoepithelioma and adenomyoepithelioma with carcinoma (malignant adenomyoepithelioma) with associated breast malignancies: A case series emphasizing histologic, radiologic, and clinical correlation

The 2012 World Health Organization (WHO) classification of breast tumors distinguishes adenomyoepitheliomas (AMEs) as benign tumors composed of a biphasic proliferation of phenotypically variable myoepithelial cells around small epithelial lined spaces. Many AMEs have demonstrated benign behavior and are often cured with excision with negative margins, but some have exhibited malignant transformation of the myoepithelial cells, ductal epithelial cells, or both. When one of the components is histologically malignant, it is termed AME with carcinoma. Due to the rarity, the literature correlating imaging, histology, and clinical outcome is limited. A retrospective review was undertaken. A review of an institutional pathology database identified 14 cases with AME or malignant AME. Most AMEs had nonspecific imaging findings and were categorized as Bi-Rads 4. Histologic features of AME did not correlate with prior or concurrent breast malignancies or any radiographic features. Clinical follow up could be obtained for all but one case (mean follow up time = 75 months). 5 cases had no known treatment post-biopsy and 5 patients received mastectomy. No recurrences were noted. 3/13 cases of benign AME had associated breast malignancies including invasive ductal adenocarcinoma and ductal carcinoma in-situ. 1 case of malignant AME had a synchronous separate malignant phyllodes tumor. Given the unclear and unpredictable propensity for malignant transformation, conservative excision with negative margins currently seems appropriate.