18F-FDG PET/CT Imaging of Pulmonary Mucinous Cystadenocarcinoma with Signet Ring Cells

Combined 18F-Fluorodeoxyglucose positron emission tomography and computed tomography (18F-FDG PET/CT) of a 63 year-old male with a recently diagnosed right upper lung mass referred for initial staging. Maximum intensity projection (MIP) image of 18F-FDG PET/CT a, axial low-dose, non-intravenous (IV) iodinated contrast CT b, axial fused 18F-FDG PET/CT c, axial full-dose, IV contrast-enhanced CT, performed 3 months prior d and axial 18F-FDG e images show a hypodense, cystic-like mass with calcifications in the anterior segment of the right upper pulmonary lobe, which demonstrates low, diffuse 18F-FDG uptake (SUVmax: 2.8) (white arrows). Multiple intensely hypermetabolic right hilar and right paratracheal lymph nodes were also noted, finding suspicious for metastatic disease (SUVmax: up to 9.3) (white arrowheads). Anatomic and metabolic appearances of the primary lung lesion were consistent with presence of mucus, pointing towards a possible diagnosis of mucinous cystadenocarcinoma, a rare variant of lung adenocarcinoma [1, 2]. Raza et al. have reported another case of mucinous cystadenocarcinoma, which also showed heterogeneous uptake in 18F-FDG PET/CT, but without nodal or pleural involvement [3