["Diagnostic" interscalene plexus block].

The dedicated target region should be systematically examined before performing an ultrasound-guided nerve block so that the anatomy can be assessed and anatomic variants or pathologic findings are not missed. In the case described an ultrasound-guided interscalene plexus block was performed in a 73-year-old man. During this examination a cystic structure was detected within the thyroid gland. The further diagnostic procedure showed a metastasis of a renal cell carcinoma which had been treated by resection 10 years before.