L-[3-18F]-α-methyltyrosine (FMT) is amino-acid tracer for positron emission tomography (PET), and is used for tumor detection because malignant tumor cells accumulate 18F-FMT based on the increased expression of amino-acid transporter. This study was conducted to investigate a usefulness of 18F-FMT PET in combination with 18F-FDG PET for the diagnosis of sarcoidosis in patients with suspected malignancy.

Inclusion Criteria:

• Eligible patients were required to have histologically proven noncaseating epithelioid cell granuloma and at least one disease that the possibility of coexistent malignancy could not be excluded as follows; 1) extrapulmonary lesions mimicking malignant diseases including systemic lymphadenopathy, hepatosplenic involvement, or other lesions, 2) multiple nodular lesions mimicking pulmonary metastasis, 3) the occurrence of BHL in cancer patient.

Exclusion Criteria:

• The patients that PET imaging using 18F-FDG and 18F-FMT was performed before establishment of the final diagnosis of sarcoidosis, patients undergoing treatment for sarcoidosis before the PET study, and patient having diabetes mellitus.