Tyrosine crystals in salivary gland tumours.

Tyrosine crystals were seen in 24 of 113 salivary gland pleomorphic adenomas from Malawi and one of six carcinomas arising in a pleomorphic adenoma; they were present in tumours from all common anatomical sites. They were not found in 71 other salivary tumours of varying histological type. Similar crystals were found in one out of 56 pleomorphic adenomas from patients operated on at St Thomas's Hospital. No excess tyrosine was demonstrated in a tumour containing many crystals. Their great frequency in black patients is confirmed but an adequate explanation for this phenomenon has not been found.