Background: With the increasing use of USG, MRI and CT, adrenal lesions are frequently found in the daily practice. These lesions may be primary or secondary in origin. However, it is important to resolve whether these lesions are benign or malignant.
Purpose: The aim of this case detection study was to compare FDG-PET CT with MRI in differentiating benign from malignant adrenal mass lesions.
Patients: All patients were admitted to our out-patient clinic between 2006 and 2010 for evaluation of adrenal mass lesions. FDG-PET CT and MRI were performed to all patients. We analyzed the laboratory data of the patients and compared FDG-PET CT results with MRI results.
Results: The study included 21 patients ((13 female, 8 male, mean age 55 years old (between 26 and 71)) with 29 adrenal lesions (mean size 2.77±1.07 cm; 16 bilateral and 13 unilateral). Five out of 29 lesions were malignant according to MRI. Three of malignant lesions on MRI were also malignant according to FDG-PET CT (SUVmax>2.5). Of the 3 malignant lesions on FDG-PET CT, 1 diagnosed as tuberculosis, 1 as primary adrenal carcinoma and 1 as atypical lipoma, according to histopathological/microbiological analysis. Six out of the 29 lesions were interpreted as benign by MRI but malignant according to FDG-PET CT (SUVmax>2.5). With further investigation, 1 of them diagnosed as adrenocortical adenoma, 1 as lung carcinoma metastasis, 1 as kidney carcinoma metastasis and 1 as tuberculosis.
In 3 patients with benign MRI appearance and SUV max <2.5 on FDG-PET CT, there were pathological FDG up-take in other locations as lung, epigastric and adnexial area, in whom further investigations revealed inflammatory processes.
Conclusion: According to our study results, FDG-PET CT is not better than MRI for differentiating malignant from benign adrenal lesions. FDG-PET CT leads to unnecessary invasive investigations in some patients. However, it could be used in detecting metastases in patients with known malignancies.