Uptake of 18F-FDG in Adrenal Adenomas Is Associated With Unenhanced CT Value and Constituent Cells

Abstract

Purpose The purposes of this study were to investigate the correlation between unenhanced CT attenuation values and 18F-FDG uptake in adrenal adenomas, and to clarify the mechanism of FDG uptake in adrenal adenomas based on immunohistochemical findings. Materials and Methods In 57 adrenal adenomas, the correlation between SUVmax on 18F-FDG PET and unenhanced CT attenuation was retrospectively investigated. In the 11 surgically resected nodules, the clear cell ratio (CCR) and expression levels of glucose transporters (GLUTs) 1 to 4 were pathologically evaluated. The GLUT expression levels were scored at 0 to 3 points for each transporter, and the sum of these expression levels was defined as the GLUT score. The relationships between CCR and either the CT attenuation number or SUVmax, and between the GLUT score and each of the CT attenutation value, SUVmax, or CCR were evaluated. Results There was a significant positive correlation between SUVmax and the CT attenuation value for the group of 57 adenomas (R = 0.44, P = 0.0007). For the 11 surgically resected cases, there was a nonsignificant trend of negative correlation between SUVmax and CCR (R = 0.57, P = 0.06). There was a significant positive correlation between GLUT score and CT attenuation value (R = 0.68, P = 0.02), and a significant negative correlation between GLUT score and CCR (R = 0.60, P = 0.003). Conclusions Adrenal adenomas composed of many compact cells or having high attenuation on unenhanced CT showed high FDG uptake. FDG uptake of adrenal adenomas may depend on the constituent cells.