The characteristics of 18F-FDG PET/CT in pulmonary cryptococcosis

Abstract

Objective To investigate the 18F-FDG PET/CT imaging characteristics and PET metabolic characteristics of pulmonary cryptococcosis (PC). Methods A retrospective study was performed in 22 patients with PC (16 male and 6 female; 34-81 years old), confirmed through etiology or pathological examination from March 2011 to October 2015. To analyze the clinical data, CT patterns (single nodule, multiple nodules, pneumonia type, and mixed type), CT signs (vessel convergence sign, spiculation sign, halo sign, air bronchogram, and lobulation), and FDG metabolic patterns(hypermetabolism and hypometabolism) of PC were analyzed. Results PC was characterized by single nodule(9/22), multiple nodules(7/22), pneumonia type (1/22), and mixed type (5/22) for the 22 patients with PC. Most of the nodules were found in the inferior lobe of the lung. There were 15 cases(15/22, 68.18%) involving one or both inferior lobe of the lungs, of which 9 cases(9/22, 40.91%) involving the right inferior lobe, 2 cases(2/22, 9.09%) involving the left inferior lobe. Vessel convergence sign(12/21) was the most common sign, followed by spiculation(10/21), halo sign(8/22), air-bronchogram sign(6/21), and lobulation(4/21) with nodules on CT scan. The maximum standardized uptake value of PC was from 1.00 to 12.67 on 18F-FDG PET/CT scan, and hypermetabolism type (20/22) was the predominant pattern. Six patients with single nodule were misdiagnosed as malignant tumors. Conclusions Most cases of PC were characterized with single and multiple nodules. A relative high rate of misdiagnosis was obtained using 18F-FDG PET/CT scan with varied standardized uptake value. Diagnosis of single nodule with high FDG metabolism in lung cancer should differentiate from PC. Key words: Pulmonary cryptococcosis; Positron-emission tomography; Tomography, X-ray computed; Fluorodeoxyglucose F18