A wrist's tale: When pain met swelling

This 15-year-old female presents with anterior right wrist pain and swelling. There is no known injury or prior surgery. Have a look at images 1 through 6, and see if you can answer the following questions.

Q1 – What is the most likely diagnosis in this 15-year-old female with a mass of the volar aspect of the forearm?

Q2 – What are the low-signal filling defects within the lesion?

Coronal T1

Coronal T1 (Post-contrast)

Coronal T2

Gradient

Axial T1

Axial T2

A1 – Venous malformation (formerly hemangioma).

Vascular anomalies are divided into two major groups. The first are vascular tumors that arise due to vascular proliferation, and are called hemangiomas. The second group of lesions are called vascular malformation, and arise because of inborn errors in morphogenesis.

Vascular malformations are classified according to the dominant distorted vessel type, and include capillary, lymphatic, and venous malformations. Vascular malformations are also categorized into low-flow and high-flow groups which is important for treatment of the lesions. Hemangiomas, on the other hand, occur in infancy, have rapid neonatal growth, and slowly involute. Venous malformations can occur anywhere in the body, and can present with pain at rest or during exertion.

A2 – Phleboliths.

Phleboliths are seen in some, but not all, venous malformations. MRI is the study of choice for evaluation of vascular malformations. Imaging of vascular malformations present as high-signal, tubular-like structures (image 9, arrows). The presence of fat could be an indicator of muscular atrophy secondary to vascular insufficiency. Gradient-echo sequences may reveal low signal related to phleboliths or hemosiderin (image 10, arrows). Variable enhancement is noted after gadolinium administration (image 8, arrows). In the orbit, venous malformations frequently overlap with lymphatic malformations (“lymphangiomas”) and vice-versa.