Dr. Doung or an immediate family member serves as a board member, owner, officer, or committee member of Musculoskeletal Tumor Society.
ABSTRACT
Vascular anomalies include vascular malformations and vascular tumors. Vascular malformations occur in approximately 0.5% of the population and are sometimes associated with syndromes. They often appear during childhood or adolescence and present with pain. MRI is helpful in diagnosis, and shows an infiltrative pattern that is often described as serpiginous. Treatment may involve sclerotherapy, which can improve symptoms in 60% to 80% of patients, or surgery, which can improve symptoms at the same reported rate of 60% to 80%. The reported recurrence rate of vascular malformations is up to 40%. Treatment for lymphatic malformations is similar to that for vascular malformations. For vascular malformations that are associated with PIK3CA mutations, sirolimus is a treatment option. The two most common vascular tumors are infantile hemangioma and hemangioendothelioma. Infantile hemangioma will self-involute. Hemangioendothelioma presents with a wide range of activity, with up to 25% exhibiting aggressive behavior.
Vascular anomalies are grouped into two categories: vascular tumors, which are produced by neoplastic cell proliferation, and vascular malformations, which are characterized by abnormal vascular channels arising from aberrant development. Historically, both tumors and malformations have been called hemangiomas, but some physicians think this usage is ambiguous and prefer to reserve the term hemangioma for certain benign neoplasms of blood vessels. It should be noted, however, that vascular malformations are associated with gene mutations and therefore may be considered neoplastic processes. Newer treatment strategies for vascular malformations using oncologic drugs that target specific pathways involving mutated genes are based on this rationale.
VASCULAR MALFORMATIONS (VENOUS MALFORMATIONS, INTRAMUSCULAR HEMANGIOMAS, AND ARTERIOVENOUS MALFORMATIONS)
Vascular malformations are grouped into low-flow lesions (venous, lymphatic, and capillary malformations) and high-flow lesions (arteriovenous malformations)1 (Table 1). They occur in approximately 0.3% to 0.5% of the population.2 Several notable syndromes are associated with vascular malformations (Table 2), including Klippel-Trénaunay syndrome, Kasabach-Merritt syndrome, Parkes Weber syndrome, and Maffucci syndrome.
a Associated with phosphatidylinositol-3-kinase (PIK3CA) gene mutation.
The most common vascular anomaly is the venous malformation.2 When intramuscular, it is often referred to as an intramuscular hemangioma. Venous malformations occur more commonly in females than in males, at a 2:1 ratio. They are present at birth, but are often identified during adolescence. The most common location is in the head and neck. In the limbs, intramuscular venous malformations are more commonly seen in the lower extremity than in the upper extremity. They can also appear intra-articularly and can lead to hemarthrosis.
Etiology
Venous malformations are suspected to be formed by ectatic vessels morphologically similar to veins. They are hormonally modulated with estrogen receptors on endothelial cells. Symptoms are exacerbated during pregnancy or times of hormonal changes.2
There are multiple genes associated with vascular malformations (Table 1). Capillary malformations have been associated with GNAQ and GNA11, common venous malformations with TEK (TIE2) and PIK3CA, and sporadic arteriovenous malformations with MAP2K1.3
Diagnosis
The patient often reports a history of painful symptoms. These symptoms vary from intermittent pain associated with swelling to mild persistent pain, which worsens with activity. Placement of the extremity with the lesion in a dependent position usually leads to an increase in the size of the mass. The lesion can be cutaneous, subcutaneous, or intramuscular. Cutaneous lesions have skin changes and bluish discoloration and sometimes the presence of varicose veins. Subcutaneous and intramuscular lesions often do not have skin changes, but they feel boggy and have poorly defined borders. Often, the lesion is softer than the surrounding musculature. Arteriovenous malformations can sometimes be pulsatile. If the lesion is intra-articular, it can cause synovial irritation and, if it bleeds, can cause hemarthrosis. The pain of hemangiomas is occasionally due to acute thrombophlebitis, which causes the lesions to be firm and exquisitely tender on palpation.
Imaging of the lesion on plain radiographs may sometimes show phleboliths (Figure 1), which probably represent calcified chronic thrombi within the vascular channels. MRI often shows a speckled, infiltrative pattern with multiple small focal areas that have high signal intensity on proton density, short tau inversion recovery, and T2-weighted images and are isointense to muscle on T1-weighted images (Figure 2, A and B). Small amounts of fat surrounding the vessels can cause scant areas surrounding the vessels to have bright signal intensity on T1-weighted images. There is often some contrast enhancement around the vessel walls of the lesion (Figure 2, C). The pattern on these images can be described as serpiginous or as resembling grape clusters or a bag of worms. MRI can often distinguish venous malformation from arteriovenous malformation in that arteriovenous malformations have a characteristic serpiginous flow void (Figure 3, A through C). Flow voids are dark on T1 and T2, and do not enhance with contrast. Angiography can also be used to characterize arteriovenous malformation (Figure 3, D through F). Although ultrasonography is not often used for diagnosis, it is helpful in distinguishing between high-flow and low-flow malformations.
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