Aggressive muscular non-Hodgkin lymphoma

Primary muscle lymphoma is a relatively rare manifestation of lymphoma, and its presentation can be similar to other inflammatory or neoplastic causes of muscle enlargement. Its appearance on PET has as yet been unreported. We report a patient who presented with right lower extremity and left deltoid swelling whose subsequent PET scan demonstrated remarkably aggressive primary muscle lymphoma with diffuse involvement in multiple, separate muscle groups.