A coronal fused PET/CT image shows a large right breast mass with a ring-like FDG uptake (arrows).

Performance of PET in Breast Cancer
– Sensitivity 89%, specificity 80%
– Sensitivity highly depends on tumor size and grade.
– Unlikely to pick up tumor less than 0.5 cm, low chance of detecting tumor less than 1 cm
– PET is less sensitive but more specific than MRI for characterizing and detecting breast lesions

– Any focal abnormal uptake of FDG should undergo further work-up (irrespective of its standardized uptake value). Note that breast cancer, in general, has lower metabolic activity than most other malignancies
– Incidentally detected breast abnormality on PET has high likelihood of malignancy
– Delayed/dual time point imaging increases sensitivity and accuracy of PET. Tumors accumulate FDG over time (normal breast tissue will not)

Differential Diagnosis of Focal FDG – Uptake in the Breast
– Inflammatory: abscess, soft tissue inflammation, TB, sarcoidosis
– Trauma: post-biopsy, hematoma, seroma
– Benign neoplasms: ductal adenoma, fibrous dysplasia, fibroadenoma (rare)

Our case: spindle cell sarcoma of the breast.

SOURCE: RiT (partner of radRounds), Submitted by Dr. Rathachai Kaewlai