Case 6

This is an MRI study of the hand and wrist, showing a large, septated multi-cystic lesion with a large solid component in the hand, insinuating between the thenar eminence and other intrinsic muscles of the hand with mass effect. The solid component of the mass is heterogeneously hyperintense on T2, with similar T1 intensity to muscle. The solid component and septa are avidly enhancing on the postcontrast images.

I do not detect invasion of the adjacent bones, and the adjacent joints are preserved.

The findings represent a neoplastic mass which is likely of synovial origin. The most likely diagnosis is synovial sarcoma.

The differential diagnosis includes a malignant fibrous histiocytoma, or a giant cell tumour of the tendon sheath (although these tend to be much smaller, related to a tendon, and show blooming artifact).

I would flag this case for discussion at orthopaedic MDT; tissue biopsy will be required.