What is This Soft Subcutaneous Nodule on the Forearm?

Case Report
A 61-year-old man presented with an intermittent soft mass on his left forearm. The lesion was present for 3 years and frequently changed in size. There was no history of trauma or infection to the area. His past medical history was significant for gout, hyperlipidemia, hypertension, obesity, obstructive sleep apnea, and type 2 diabetes. Cutaneous examination revealed a soft, blue, 10 mm x 10 mm, compressible, painless, subcutaneous nodule on the proximal extensor aspect of his left forearm (Figure 1). The nodule was most prominent when he held his arm down and resolved when his arm was raised. 

What Is The Diagnosis?
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Diagnosis: Spontaneous Superficial Venous Aneurysm 

A venous aneurysm is a localized dilatation of the venous intima, media, and adventitia that is adjacent to a venous structure with a normal diameter.¹ Venous aneurysms are typically not associated with significant comorbidities; however, thrombosis and pulmonary embolism may occur.^2-4

Arterial aneurysms are defined as permanent, localized dilatation more than one and a half times the size of the diameter of a contiguous normal artery; however, the definition of a venous aneurysm—including the transition point from a dilatation to an aneurysm—is imprecise.⁵ For instance, researchers have previously suggested one and a half to three times the normal vein diameter as cutoffs for venous aneurysms.^6,7

Venous aneurysms can be categorized as superficial or deep. Superficial venous aneurysms may present in the cephalic and basilic systems of the upper extremities and saphenous system in the lower extremities.⁷ Deep lesions typically present in the femoral system.⁷ Compared to superficial venous aneurysms, deep venous aneurysms have a higher association with thromboembolism.²

Epidemiology
The incidence and prevalence of venous aneurysms remain unclear. In a single-center, retrospective analysis of almost 2,000 patients registered in a vascular surgery service over a period of 22 years, 30 (>1.5%) patients were found to have venous aneurysms.⁸ Among those 30 patients, nine (>0.45%) had superficial venous aneurysms. Another single-center study of 366 patients found 65 superficial saphenous vein aneurysms in 43 patients (11.7%).¹ Additionally, there is no age or gender predilection for venous aneurysms.⁸  

Clinical Presentation
Superficial venous aneurysms present as soft, compressible, nonpulsatile, mobile, subcutaneous nodules with a size that is dependent on position (Figures 1 and 2). When a lesion on the upper extremity is raised above the level of the heart, the nodule may flatten or decrease in size (Figure 3). Jugular venous aneurysms may increase in size with the Valsalva maneuver.

Pathology
Microscopic examination of a venous aneurysm will show focal dilatation involving all three major layers of the venous wall. Additionally, there may be a loss of elastic fibers, hyalinization of the intima, the presence of inflammatory lymphocytes, and, in rare instances, thrombus formation.⁹ However, a biopsy is not required to establish the diagnosis.

Differential Diagnosis
Superficial venous aneurysm, based on its presentation and location, may mimic subcutaneous soft tissue tumors, other vascular lesions, or hernias. The differential diagnosis for a subcutaneous venous aneurysm includes angiokeratoma, arterial aneurysm, arteriovenous malformation, blue nevus, lipoma, varicocele, venous lakes, venous malformation, and venous pseudoaneurysm.⁷  

Pathogenesis
Venous aneurysms can be congenital or acquired. Congenital venous aneurysms have been associated with Klippel-Trenaunay syndrome, which is a rare condition affecting vascular development.¹⁰ Acquired venous aneurysms are typically secondary to degenerative changes, infection, trauma, or venous insufficiency.⁹ In addition, superficial venous aneurysms of the saphenous vein are more common in men with high body-mass indices.¹ 

Diagnosis
Evaluation for superficial venous aneurysms may include a venous duplex ultrasound study to assess for size, shape, and the presence of thrombi; magnetic resonance imaging or computerized tomography (CT) may also be used as additional work-up studies.⁷ A potential venous aneurysm should be assessed in relationship to the normal diameter of the contiguous, normal vein. An ultrasound study would reveal an easily compressible, well-defined, heterogeneously echoic mass connecting into a normal venous structure with a lack of pulsation.¹¹ CT scan to assess superficial venous aneurysm of upper extremities is not commonly performed; however, it would show homogeneous enhancement.¹¹  

Treatment
Compared to abdominal or thoracic venous aneurysms, superficial lesions in the extremities are unlikely to rupture; therefore, surgery should be considered for a superficial venous aneurysm if a lesion is growing, disfiguring, or painful.¹² If a patient is asymptomatic, then venous aneurysms can be clinically monitored. Patients should be advised to return for additional evaluation and possible treatment if there is an increase in size, pain, edema, overlying skin changes, or symptoms particularly suggestive of a serious thromboembolic event such as pulmonary or paradoxical embolism.

Our Patient
After the completion of his clinical evaluation, our patient was reassured of the benign nature of his superficial venous aneurysm. Given his asymptomatic findings, the patient decided against a surgical excision of his lesion. He will be periodically observed for potential complications.

Conclusion
Venous aneurysms are typically benign vascular lesions that occur in both men and women with or without a history of trauma in the site of occurrence. Superficial venous aneurysms are diagnosed clinically and appear as a soft, mobile, nonpulsatile subcutaneous nodule that change in appearance depending on position. Ultrasound imaging may be used to assess the lesion and to look for concerning features such as the presence of a thrombus. Potential complications of both deep and superficial venous aneurysms include pulmonary embolism. Asymptomatic superficial venous aneurysms may be managed conservatively with observation; symptomatic or cosmetically concerning lesions can be removed surgically. 

Ms Kim is a medical student at Stanford University School of Medicine in Stanford, CA. Dr Cohen is an adjunct professor of dermatology at Touro University California College of Osteopathic Medicine in Vallejo, CA, and a dermatologist at San Diego Family Dermatology in National City, CA.

Disclosures: The authors report no relevant financial relationships.  

References
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