The many faces of sarcoidosis: asymptomatic muscle mass mimicking giant-cell tumor.

Sarcoidosis is a chronic, multisystem granulomatous disease of unknown etiology. Muscle involvement is frequent, but often asymptomatic. There are three forms of muscular sarcoidosis: only the nodular type can be recognized by imaging. MRI and 18F-FDG PET-CT are the best methods to attempt the diagnosis of nodular muscular sarcoidosis; nevertheless, the lesion can mimic a malignant tumor. In this case, biopsy is the only tool to identify the disease.