Diagnosis
The pediatric hematologist and oncologist is often called upon to distinguish between malignant versus benign masses, and vascular anomalies should be on the differential of a new onset mass. Clinical examination combined with imaging can generally lead to a diagnosis and rule out malignancy. Experienced clinicians and radiologists familiar with these entities are optimal. If unusual features are present on physical exam or imaging, or if concerning clinical history is present, biopsy must be considered. Caution must be taken with biopsy of vascular lesions given their propensity to bleed.
Under ultrasound examination, VMs appear as heterogeneous lesions typically containing anechoic vascular channels. The lesions are compressible if near the skin surface. VMs demonstrate slow flow, and Doppler analysis typically shows minimal to no color flow that can be augmented upon releasing compression or with Valsalva maneuvers. Spectral analysis reveals no waveforms or a monophasic venous waveform (16,17). If Doppler does not demonstrate color flow and/or spectral waveforms, flow within the malformation may be too slow for sonographic detection, or vessels may have thrombosed (18). Slow blood flow contributes to the development of phleboliths, which are painful thrombosis and a common occurrence of VMs. On exam, they are palpated as hardened nodules (19). On US, they appear as a hyperechoic foci with posterior shadowing and are considered pathognomonic for VM (20).
As in this patient, on magnetic resonance imaging (MRI), VMs appear hyperintense on T2 weighted images (Fig 2). On T1 weighted images, they appear iso- or hypointense but may contain hyperintense areas representing blood products, fat, or calcifications. VMs enhance on T1 weighted images obtained after intravenous contrast administration. MRI not only aids in the classification of vascular malformations, but it also can determine lesion extent and relationship to surrounding structures (21,22).