We experienced a rare case of the ulnar nerve palsy caused by the compression of the cyst arising from the flexor carpi ulnaris fascia.
The patient was a 60 years old male and had hypesthesia at the right ring and little fingers. The ulnar nerve was compressed by the cyst which was multilocular, 11.5×4.0×3.0cm in size and contained yellow jelly fluid. This cyst arouse from the flexor carpi ulnaris fascia near the medial epicondyle and there could not be found any comminucation with the joint capsule.
Microscopically, the cyst wall was composed of dense collagen fibers and no muscle fibers were seen.
