Transiently Altered Distribution of F-18 FDG in a Patient with Subacute Thyroiditis

A 57-year-old female with pulmonary adenocarcinoma was referred for F-18 FDG PET/CT as part of a staging workup. Maximal intensity projections (MIP) view (a) and coronal view (b) showed diffuse symmetrically increased skeletal muscle uptake and relatively decreased hepatic uptake. In addition, intense hypermetabolism was demonstrated in both thyroid lobes. The maximal standardized uptake values (SUVmax) of the thyroid gland, liver and psoas muscle were 8.9, 2.3 and 1.7, respectively. However, the primary malignancy, metastatic lymphadenopathies in the neck, supraclavicular, mediastinum and abdominal areas were identified without any difficulty. On the 6-week follow-up F-18 FDG PET/CT images (c, d), the primary malignancy and metastatic lymphadenopathies showed partial metabolic response after 2 cycles of chemotherapy with pemetrexed and cisplatin. Also, increased uptake of the skeletal muscle and decreased uptake of the liver were normalized. The SUVmax of the thyroid gland, liver and psoas muscle were 2.8, 3.4 and 1.0, respectivel