Primary apocrine carcinoma of the breast incidentally detected on CT angiography: Imaging–pathology correlation in a rare histologic subtype

Apocrine carcinoma (AC) of the breast is a rare histologic subtype characterized by apocrine morphology and a frequent androgen receptor (AR)-positive / estrogen receptor (ER)-negative profile. Imaging findings are often nonspecific, making diagnosis challenging. We report an incidental 1.0-cm apocrine carcinoma (Elston–Ellis grade 2) detected in a 72-year-old woman during thoracic CT angiography. Retrospective review identified a small enhancing lesion in the right breast. Mammography (CC and MLO views) demonstrated an irregular high-density mass with indistinct margins. Targeted ultrasound revealed an irregular hypoechoic mass with noncircumscribed margins (BI-RADS 4A). Due to limited access to image-guided core biopsy, an excisional biopsy was performed. Histopathologic examination confirmed invasive apocrine carcinoma with an in situ component and AR positivity. The patient subsequently underwent therapeutic mastectomy. This case highlights the nonspecific imaging features of AC and emphasizes the key role of histopathology and immunohistochemical profiling in diagnosis and management.