FDG PET/CT reveals the primary tumor in a patient with occult breast carcinoma undetected by other modalities.

: A 54-year-old woman presented with left axillary adenopathy for 6 months. Biopsy result was consistent with nodal metastases of breast carcinoma: estrogen receptor (negative), progesterone receptor (negative), and Her-2 (negative). The primary breast tumor, however, could not be detected on breast ultrasound, mammography, and magnetic resonance imaging. F-FDG PET/CT revealed a mildly FDG-avid nodule in her left breast, consistent with primary tumor. She received neoadjuvant chemotherapy followed by modified radical mastectomy. The case demonstrates the usefulness of FDG PET/CT in evaluating patients with breast cancer, even when the primary tumor remains undetected by other modalities.