Triple-Negative Breast Cancer Coexisting with Adenomyoepithelioma: A Case Report

Adenomyoepithelioma (AME) is a rare breast tumor characterized by the proliferation of both inner epithelial and outer myoepithelial cells. Here, we report a case of AME coexisting with triple-negative breast cancer (TNBC) in a 55-year-old woman. Mammography revealed an obscured oval mass measuring approximately 1 cm, with artificial intelligence-computer-aided detection showed an abnormality score. US revealed a mass with a heterogeneous echogenic pattern. AME was diagnosed by external biopsy; our pathology review raised a high suspicion of malignancy, prompting surgical excision. Breast-specific gamma imaging, performed at the surgeon's request, demonstrated increased radiotracer uptake. Preoperative MRI revealed a rim-enhancing mass with rapid initial enhancement and delayed washout. A lumpectomy was performed. The final diagnosis confirmed the coexistence of AME and TNBC, which is rare. Even when benign AME is diagnosed through preoperative core needle biopsy, suspicious imaging findings should warrant surgical excision.