Abnormal 18F-fluorodeoxyglucose (FDG) uptake in muscle tumors on PET-CT: A pictorial atlas of pathologic findings

Learning Objectives 1. Demonstrate the scintigraphic appearance of abnormal muscle 18F-FDG uptake in a variety of primary muscle tumors, metastases to muscle, leukemia and lymphoma involving musculature. 2. Illustrate the additional value of CT in localizing pathologic findings to muscle. 3. Discuss a classification of muscle tumors and clinical presentation. 4. Improve the ability and level of confidence of nuclear medicine physicians in interpreting PET-CT.

This educational exhibit showcases illustrative examples of pathologic 18F-FDG uptake in primary muscle tumors, metastases to muscles and other uncommon malignant processes e.g. muscle lymphoma. Because muscle uptake can be physiologic, recognizing the differences in scintigraphic appearance between normal and abnormal muscle is critical. In this presentation we discuss mechanisms of 18F-FDG muscle uptake and various patterns helpful to distinguish physiologic from pathologic muscle activity. The addition of CT aids in anatomic localization and morphologic delineation of the structures being reviewed and its contribution to diagnosis will be highlighted. The presentation will provide a classification of malignant tumors involving muscles and common clinical presentations. Skeletal muscle is an unusual site of metastasis and practitioners may not be familiar with associated patterns of imaging. An understanding of normal versus pathologic patterns of muscle FDG uptake, and recognition of abnormal features by their metabolic and CT appearance is vital for correct image interpretation