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Nuclear Medicine

E3083. Differential Diagnosis and the Next Step: Incidentally Detected FDG-Avid Breast and Axillary Lesions

Jahangir K,  Dashevsky B,  Pu Y,  Abe H,  Kulkarni K. The University of Chicago, Chicago, IL

Address correspondence to K. Jahangir (

Background Information: PET/CT is the mainstay for staging and follow-up of many malignancies, including melanoma, lymphoma, colorectal, and non–small cell lung cancers. Some studies have shown FDG-avid breast lesions to represent a second primary malignancy in up to 54% of cases. In addition, while FDG PET/CT is not sensitive for nodal metastases, if lymph nodes are FDG-avid, there is high positive predictive value for malignancy. Thus, identifying FDG-avid breast and axillary lesions, and determining appropriate follow-up imaging and management is imperative. Here we review tips and pitfalls related to imaging and follow-up of incidentally detected breast and axillary FDG-avid lesions.

Educational Goals/Teaching Points: Our exhibit will review benign and malignant causes of incidentally detected FDG avid breast and axillary lesions, imaging findings and appropriate work-up.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Incidentally detected breast lesions include benign (inflammatory [diabetic mastopathy, foreign body reaction, etc.], infectious [mastitis, abscess]) and malignant (new primary vs metastasis or recurrence) pathologies. We review breast anatomy, patterns of spread of malignancies commonly staged on PET/CT, and associated findings that may influence diagnosis. Incidentally detected FDG-avid axillary lesions include nodal metastases, reactive adenopathy, primary lymphoma, and other inflammatory/infectious etiologies. We review nodal anatomy, staging of malignancies which commonly spread to the axillary lymph nodes, ultrasound findings suggestive of metastatic involvement, and when to suspect a second primary malignancy. In addition, imaging findings, follow-up, pathology, and management of several representative cases for both incidentally detected FDG-avid breast and axillary lesions are reviewed.

Conclusion: Familiarity with FDG-avid benign and malignant breast and axillary lesions is essential to determine appropriate follow-up and treatment.