The biopsy specimen demonstrated a large, ectatic vein, lined by a single layer of endothelium, with surrounding thin connective tissue. Notably, inflammation was not present, and no glomus cells were seen.
Venous aneurysms are cutaneous vascular malformations that represent localized saccular anomalies of preexisting veins.1 Their blue color is partially attributable to deoxygenated blood within the aneurysm and partially the result of the Tyndall effect. They are generally benign and may be solitary or multiple, in which case they are often grouped. The lesions vary in size from barely perceptible ectasias to large, disfiguring cavernous lesions that may compress internal structures. They are usually well defined and round, with a smooth surface that is easily compressible and promptly refills when pressure is released. Most venous aneurysms are asymptomatic, but they may become painful as a result of slow enlargement and pressure on surrounding structures, especially nerves. The cause of the lesions is unknown, but they may be the result of external trauma to the venous architecture.1
A Painful Blue Nodule on the Dorsum of the Hand—Diagnosis. Arch Dermatol. 2004;140(11):1393-1398. doi:10.1001/archderm.140.11.1393-h