Keywords
lipoma - intravenous lipoma - intra- and extravascular lipoma - brachiocephalic vein - intravascular tumor
Introduction
Lipomas are benign, well-differentiated tumors made up of adipocytes and are the most common type of soft tissue mass.[1] They can appear anywhere in the body but are most commonly found in the subcutaneous tissue of the upper half and proximal limbs. Primary venous tumors can occur anywhere on the body and the walls of the veins are rarely the site of the origin of the neoplasm. Intravascular lipoma is very rare and occurs most often in the inferior vena cava,[2] and a review of the literature found only a few isolated case reports involving the superior vena cava[3] and subclavian veins,[4] as well as innominate veins,[5] internal jugular veins, femoral veins,[6] and renal veins.[1]
In this article, we addressed a unique instance of intra- and extravascular lipoma involving the right subclavian and brachiocephalic veins, as well as insights on differential diagnosis and treatment methods.
Discussion
Background
The pathology literature proposes two theories to explain this unusual presentation[4]: the mass could originate in the vein wall or in the fatty perivascular tissue. Initially, the tumor develops into the vein wall, projecting outside and inside the lumen. The second concept argues that the tumor starts from the perivascular tissue, infiltrates the vein wall, and eventually protrudes into the lumen which is an unusual site for a benign tumor.
Clinical Perspective
Although extremely rare, clinical implications of extra- and intravascular lipomas include venous compression or obstruction.
It is important to differentiate intravascular lipomas from other fat-containing intravascular malignant masses like liposarcomas, which appear more heterogeneous on imaging due to the presence of nonadipose components.[7]
Imaging Perspective
CT often reveals a well-defined, smooth ovoid, nonenhancing, hypoattenuating mass that corresponds to fat density. Intravenous contrast reveals a filling defect, indicating the lipomas' intraluminal location. On magnetic resonance (MR) imaging, these lesions present as nonenhancing, T1 and T2 hyperintense lesions that cancel out on fat-subtraction imaging. MR imaging is also beneficial in identifying simple lipoma from its near differentials, such as liposarcoma with the greatest sensitivity.[8]
Angiography is typically used to determine the extent of obstruction and the presence of any venous collaterals. However, angiography is not usually performed if other imaging modalities reveal no significant vascular obstruction.
Outcome
The literature on the treatment of extra- and intravascular lipomas varies. Biopsy has often been deemed unnecessary when imaging clearly shows a fat-attenuating mass lesion composed exclusively of fat and the patient is asymptomatic. Surgical resection is usually recommended only if the patient is symptomatic and/or shows signs of venous obstruction.[9]
In the present instance, the lesion exhibited no substantial symptoms of venous blockage or the presence of venous collaterals, and there was no evidence of malignant potential on imaging. As a result, the decision was made to treat the case cautiously adopting surveillance. A repeat CT scan after 3 months revealed no change in the size or shape of the lesion ([Fig. 5A and B]).
Fig. 5 (A and B) Follow-up imaging after 3 months shows no significant interval changes in the size or morphology of the tumor.
