Background: Somatostatin receptor positron emission tomography (SSTR-PET) with radiotracers such as 68Ga-DOTATATE, 64Cu-DOTATATE, and 68Ga-DOTATOC represents the mainstay of molecular imaging for neuroendocrine tumors (NETs). Breast findings on SSTR-PET are rare: the rates of radiotracer-avid breast lesions and incidental non-NET breast findings have been reported at 1.1% and 0.3%, respectively. Although SSTR-PET has high sensitivity and specificity for detection of NETs, incidental breast findings on SSTR-PET can present a diagnostic challenge. Metastatic NETs to the breast are rare and represent only 1-2% of non-primary breast malignancies, whereas approximately 50% of primary breast malignancies express SSTR. In addition, benign breast lesions and physiologic radiotracer uptake may be seen on SSTR-PET. In this educational exhibit, we illustrate a spectrum of benign and malignant diagnoses to help readers become more familiar with breast findings on SSTR-PET.
Learning Objectives: • List physiologic, benign, and malignant causes of radiotracer uptake in the breast on SSTR-PET. • Become familiar with the imaging appearances of breast findings on SSTR-PET. • Identify helpful features for interpretation of breast findings on SSTR-PET. • Correlate breast findings on SSTR-PET with other imaging modalities.
Abstract Content/Results: The presentation is in the form of a pictorial review. The examples will be organized into four categories. First, physiologic radiotracer uptake in normal breasts, asymmetric breast tissue, gynecomastia, and lactating breasts will be shown. Second, fibroadenomas and post-surgical inflammatory changes will be shown as benign breast lesions. Third, invasive ductal, invasive lobular, and metastatic breast cancers will be shown. Finally, metastatic intestinal and pulmonary NETs to the breast will be shown. Approximately 20 examples will be shown in total, with available correlative imaging.
Conclusion: A spectrum of physiologic, benign, and malignant breast findings may be seen on SSTR-PET. Distinguishing between benign breast lesions, primary breast cancers, and metastases on SSTR-PET can be facilitated by taking into account the patterns of radiotracer uptake, anatomic imaging findings, and temporal changes, but tissue sampling is often required. An incidental breast lesion on SSTR-PET should not be easily dismissed as a metastasis or fibroadenoma without consideration of primary breast cancer.