Incidental case of an idiopathic pulmonary arterial aneurysm masquerading as a stable pulmonary nodule for 17 years

A true pulmonary arterial aneurysm is the dilation of all three vascular walls in a pulmonary artery. True pulmonary arterial aneurysms are very rare, and the relatively minor cases on this topic present with symptoms pertaining to the causes of trauma, Behçet’s disease, pulmonary vasculitis, granulomatous lung infections, and cartilage instability. A rupture of the pulmonary arterial aneurysm can be life-threatening and often requires surgical repair. Our case presents a 70-year-old male who was referred to pulmonary clinic for evaluation of an asymptomatic, incidental finding in his right lower lobe that was considered to represent a pulmonary nodule based on its presentation on computed tomography imaging. The referring provider had requested a possible biopsy. Before proceeding with a biopsy, the presence of the pulmonary aneurysm was confirmed only after the fluorodeoxyglucose-positron emission tomography scan and a computed tomography angiography were performed. Our case illustrates the importance of including pulmonary aneurysm in the differential during work-up of a pulmonary nodule, as diagnostic sampling could have been detrimental.