Vascular and Interventional RadiologyE3324. Intravascular Lipomas: Case Report and Review
Tse G. University of California Davis Medical Center, Sacramento, CA
Address correspondence to G. Tse (firstname.lastname@example.org)
Background Information: A lipoma is the most common soft tissue mass consisting of mature adipocytes and most often arising from subcutaneous tissues of the upper half of the body and upper extremities. Intravascular lipomas are particularly uncommon and most often have been described in association with the inferior vena cava. Even more rare, intravascular lipomas have been described in association with the superior vena cava and common femoral vein. We present the first case of an intravascular lipoma of the portal vein and review the incidence, clinical presentation, and imaging appearance of intravascular lipomas.
Educational Goals/Teaching Points: We review the incidence and differential diagnosis of intravascular lipomas, discuss how patients present with intravascular lipomas, and describe the imaging appearance and pathophysiology of intravascular lipomas.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Intravenous lipomas are extremely rare tumors. Overall, intravenous primary tumors are quite rare with the most common tumors being leiomyomas and leiomyosarcomas. Intravenous lipomas have been described to arise from the inferior vena cava, the superior vena cave, and common femoral vein. Intravenous lipomas on CT should demonstrate fat attenuation, lack of internal enhancement, and preferably, an acute angle formed with respect to the venous wall with a ring of peripheral surrounding contrast since an extraluminal lipoma causing venous compression is also possible but would be seen with obtuse angles as classically taught in radiology. Ultrasound is not preferable in the evaluation of intravenous lipomas because it cannot fully evaluate the extent of venous involvement when compared to CT or MRI. This is important if surgical resection is considered and to confirm its intraluminal location. Moreover, intraluminal lipomas present as nonvascular iso- to hyperechogenic masses on color Doppler and grayscale ultrasound, sonographic features which overlap with a venous thrombus. MRI can further aid in the diagnosis by demonstrating high signal intensity on T1-weighted images, intermediate to high signal on T2-weighted images, and uniform signal dropout on fat-suppressed images, supporting the diagnosis of lipoma.
Conclusion: This is the first known report of an intraluminal portal vein lipoma. Most reported cases are incidentally discovered while a few present with obstructive symptoms. Pathophysiologically, lipomas may conceivably originate from mesenchymal stem cell differentiated adipocytes that reside in the tunica adventitia. Imaging with CT and MRI both play a critical role in confirming the diagnosis where the tumor should follow fat density and signal intensity on all series and may help in differentiating from primary tumors, secondary tumors, and thrombi.