A ‘bag of worms’ in a foot

A 12-year-old girl presented with a slightly painful swelling on the dorsum of the right foot. The patient reported a trauma three months before, involving the same region.

Physical examination revealed a soft mass in the first intermetatarsal space, mildly painful upon compression. The skin around the swelling appeared normal (Figure 1).

Figure 1.

Physical examination revealed a soft tissue mass in the first intermetatarsal space, on the dorsal region of the right foot (arrows).

The patient underwent conventional radiographs which were negative and subsequently was referred for a magnetic resonance imaging (MRI) that showed a mass (with a 4.5 cm maximum diameter) containing dysplastic and tortuous blood vessels (Figure 2). No solid tissue was detectable within the mass. This imaging appearance, resembling a ‘bag of worms’ is characteristic of vascular malformations (VM), initially described in brain lesions (especially in arteriovenous malformations) (1). The lesion presents increased signal intensity on water sensitive sequences due to low-flow fluid, characteristic of a venous VM (V-VM).

Figure 2.

Magnetic Resonance Imaging, T2-weighted sequence with fat suppression (water sensitive sequence—frontal view on the right, axial view on the left), showed a mass in the first intermetatarsal space, composed of dysplastic and tortuous blood vessels (arrows) without solid tissue detectable.

Therapeutic options were discussed with the patient and her parents. Because of the benign imaging features of the lesion, and mild clinical symptoms, it was decided to avoid biopsy or invasive treatment of the lesion. Clinical and radiological follow up with MRI after 6 months showed no change in the size and appearance of the lesion.

Vascular malformations are a large group of congenital anomalies that are thought to be present at birth, although not always evident at that time (2). In 1982, Mulliken and Glowacki introduced a classification system of vascular anomalies that was later revised and adopted by the International Society for the Study of Vascular Anomalies (ISSVA) (3–5). The ISSVA classification is now widely accepted. This system divides vascular anomalies into two main broad biologic categories: vascular/vasoproliferative neoplasms and vascular malformations (5).

Venous vascular malformations usually grow proportionally with the child without regression (2). Their growth can be exacerbated due to hormonal changes or as a result of thrombosis, infection, trauma, or incomplete resection (2). They may be infiltrative and involve multiple tissue planes, as in the case we present (2).

Venous vascular malformations are the most common type of congenital vascular malformation (6). They may occur anywhere in the body, including the head and neck (40%), extremities (40%), and trunk (20%) (6). MRI or compression ultrasound with Doppler evaluation is usually sufficient for making the diagnosis (2, 6).

Several treatment strategies may be performed in symptomatic patients including surgical resection, elastic compression, medication (sirolimus), and interventional radiological procedures (by means of sclerosing agents or cryoablation) (6,7). Treatment is individualized, given the diversity in presentation, symptomatology, location, and extent of V-VM (6).

This educational case highlights the importance of pathognomonic imaging signs (the ‘bag of worms’ appearance on MRI) to diagnose this benign condition. Moreover, the severity of the patient’s symptoms is crucial in shared decision making (follow-up versus treatment).

Funding: There are no funders to report for this submission.

Potential Conflicts of Interest: All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.