Mimicry of physiological urinary FDG excretion: squamous cell carcinoma of esophagus metastasizing to psoas muscle.

Skeletal muscle metastases are rare and usually occur with various malignancies at more advanced stages. FDG PET/CT has been known as a useful tool to detect these lesions because of the character of whole-body scanning and superior contrast between malignant and normal tissues, except in areas with abundant physiological FDG radioactivity, such as the urinary system. We present a patient with esophageal squamous cell carcinoma and an incidental, rare finding of psoas muscle metastasis that was initially omitted because of the similarity of its distribution to physiological urinary FDG excretion in the ureter.