Pericardial lipoma encasing the right coronary artery: a multimodality imaging case report.

BACKGROUND: Pericardial lipomas are rare, benign cardiac tumors. Encasement of a coronary artery by such a tumor is extremely uncommon and significantly elevates surgical risk. We report the first case in which multimodality imaging clearly demonstrates a pericardial lipoma enveloping the right coronary artery (RCA) without luminal stenosis, adding a novel anatomical observation to the literature. CASE PRESENTATION: A 32-year-old woman presented with a one-year history of exertional chest tightness and dyspnea that had worsened over three days. Physical examination and laboratory tests were unremarkable except for elevated thyroid-stimulating hormone (13.26 μIU/mL). Echocardiography revealed a 7.8 cm hypoechoic mass above the aortic root with a segment of the RCA coursing within it; color Doppler showed no flow disturbance. Contrast-enhanced cardiac computed tomography (CT) and cardiac magnetic resonance (CMR) confirmed a homogeneous fat-density mass (CT attenuation -85 HU, no enhancement, complete signal suppression on STIR) consistent with a pericardial lipoma. The tumor measured 5.5 cm in maximum transverse diameter and was seen to completely encase the RCA without stenosis. A diagnosis of pericardial lipoma with RCA encasement and concomitant subclinical hypothyroidism was made. After multidisciplinary discussion, levothyroxine was initiated and a staged plan including preoperative coronary angiography followed by surgical resection with RCA protection was formulated. The patient's symptoms resolved at discharge. At one- and three-month follow-ups she remained asymptomatic, but she subsequently declined all further contact and was lost to follow-up; no adverse cardiac events were recorded during the observation period. CONCLUSION: Pericardial lipomas can encase a coronary artery while maintaining luminal patency due to the compliance of adipose tissue. When a pericardial mass is detected on echocardiography, the coronary course must be actively traced. Multimodality imaging with CT and cardiac magnetic resonance (CMR) is essential for delineating the tumor-artery relationship and guiding surgical strategy. Coexisting endocrine disorders should be corrected preoperatively. Although the loss of long-term follow-up limits our conclusions, the imaging findings themselves provide an important cautionary lesson.