Schwannoma of the brachial plexus presenting as an enlarging cystic mass: report of a case.

We report a rare case of schwannoma of the brachial plexus presenting as an enlarging cystic mass. A 52-year-old woman was found to have a rapidly enlarging cystic lesion in the left pectoralis minor space. Surgical exploration finally found that the lesion was schwannoma originating from the fascicles of the brachial plexus. Partial removal of the fluid enabled us to dissect the mass without difficulty. The patient showed no sign of neurological disorders postoperatively. Although schwannoma sometimes accompanies the cystic lesion in part, schwannoma of the brachial plexus manifesting as a cystic lesion is very rare.