2-Deoxy-2-[18F]fluoro-D-glucose positron emission tomography uptake in a giant adrenal myelolipoma

Incidental adrenal lesions found on anatomic imaging are not uncommon. 2-Deoxy-2-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) imaging is highly accurate in the differentiation of benign from malignant adrenal lesions, both in patients with proven malignancy and with adrenal lesions detected incidentally. A 60-year-old white female with a history of lower mid-back pain underwent computerized tomography (CT) imaging that identified a 15-cm complex mass within the left adrenal gland with soft tissue, cystic, and adipose components. FDG-PET imaging showed significant hypermetabolic activity within portions of the mass with central photopenia suggesting a malignant lesion with central necrosis. Surgical excision and pathological examination, however, revealed a benign adrenal myelolipoma with extensive adenomatous and hematopoietic elements. Prior reports of adrenal myelolipoma evaluated with FDG-PET imaging have described no significant FDG uptake within these benign tumors. This case is an unusual example of histologically proven benign adrenal myelolipoma that was hypermetabolic on FDG-PET imaging. Correlation of pathologic and imaging findings demonstrated that the hypodense regions on CT were hypometabolic on FDG-PET and corresponded to cystic necrosis and adipose elements, whereas the adenomatous and hematopoietic elements were hypermetabolic.