A Rare Case of Invasive Apocrine Carcinoma of the Breast with Unusual Radiologic Findings

Invasive apocrine carcinoma (IAC) of the breast is a rare subtype of breast malignancy. Its incidence is not well known, but it is approximately less than 1% to 4%. For these reasons, there are few reports and little information on the radiologic appearance of IAC. Furthermore, most of the case reports show malignant features which are similar to invasive ductal carcinoma (IDC). We present a rare case of IAC without typical malignant feature on mammography, and ultrasonography (USG). Imaging findings on computed tomography (CT), magnetic resonance imaging (MRI), and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT are also presented. The nodule in our case showed a relatively benign feature on USG and it is the first case of IAC with unusual findings. Therefore, this report may encourage radiologists to consider the malignant potential and perform pathologic correlation even if a newly developed nodule does not present with a typical malignant feature on USG.