A Case of Adenomyoepithelioma of the Breast Showing Strong Uptake of 18F‐Fluorodeoxyglucose on a Positron Emission Tomography

An adenomyoepithelioma of the breast is a rare tumor characterized by biphasic proliferation of both epithelial and myoepithelial cells. This tumor is generally considered as a benign neoplasm, and there are few reports describing the imaging features of this tumor through ¹⁸F‐fluorodeoxyglucose positron emission tomography (FDG‐PET). Here, we report a case of an adenomyoepithelioma that showed strong uptake of FDG on PET similar to that observed with a malignant tumor. A 73‐year‐old woman presented to our hospital with a 3.5‐cm, mobile, and elastic hard tumor in the upper area of the left breast. Although the findings of mammography, ultrasonography, and contrast‐enhanced magnetic resonance imaging suggested that the tumor was malignant, it was diagnosed as an adenomyoepithelioma by core needle biopsy. An invasive ductal carcinoma, 0.5‐cm in size, was detected in the medial upper area of the ipsilateral breast during an examination. Although FDG‐PET demonstrated no lymph node or distant metastases from the invasive ductal carcinoma, strong uptake of FDG was detected in the adenomyoepithelioma. Breast conserving surgery and sentinel lymph node biopsy for the invasive ductal carcinoma together with resection of the adenomyoepithelioma was performed. A diagnosis of adenomyoepithelioma was confirmed through histologic examination of the resected specimen. This case indicates that some adenomyoepitheliomas may show a strong uptake of FDG on PET, which resembles a malignant tumor.