Hand mass There is a lobulated mass centered within the webspace between the index and middle fingers volarly measuring 1.5 x 4 cm in the transverse and longitudinal dimensions, respectively. The proximal margin of the mass lies at the level of the second and third metacarpal necks between the flexor tendons of the index and middle fingers and volar to the transverse metacarpal ligament. The mass extends distally into the base of the middle finger along the radial aspect of the A2 pulley. The mass also appears to extend along the course of the neurovascular bundle, and does not appear to arise directly from a tendon. It is predominantly isointense to skeletal muscle with small foci of increased signal centrally which may reflect small foci of hemorrhage or slow flowing blood. On T2 sequences, the mass is more heterogeneous but predominantly hyperintense to skeletal muscle with small tubular foci of low signal which may reflect flow voids. There is prominent enhancement following administration of gadolinium. No additional masses are identified. A small focus of abnormal signal is noted in the third metacarpal head which does not enhance and may represent a cyst. Tiny focus of fluid signal is noted between the flexor tendon and neck of the third proximal phalanx which could represent fluid in the tendon sheath or a small ganglion. This also does not enhance.
Hand mass as detailed above. The mass does not demonstrate signal characteristics consistent with lipoma or cyst. Although nonspecific in nature, the lobulated contour and close proximity to the neurovascular bundle suggests the possibility of a vascular malformation. A nerve sheath tumor or tenosynovial giant cell tumor are also in the differential diagnosis but considered to be less likely etiologies.