Kit protein expression and analysis of c-kit gene mutation in Adenoid Cystic Carcinoma
The c-kit proto-oncogene encodes a transmembrane receptor tyrosine kinase (KIT), which is expressed in several normal human tissues, especially mast cells and interstitial cells of Cajal. Expression of KIT has been noted in several types of neoplasms and gene mutation has been shown as a mechanism of c-kit oncogene activation in some tumors. Recently, a single adnexal adenoid cystic carcinoma (ACC) was reported to demonstrate KIT expression, however, examination of KIT expression or c-kit mutation in ACC of salivary glands has not been performed. We examined archival tissue samples from 30 ACC of major and minor salivary glands for KIT protein expression by immunohistochemistry with a polyclonal antibody and c-kit gene mutation by polymerase chain reaction amplification and DNA sequencing. KIT protein expression was noted in 90% of ACCs. An association between the presence of at least 50% KIT positive neoplastic cells and Grade 3 ACC or a solid growth pattern was observed (P < .05). KIT expression in normal or nonneoplastic salivary gland tissue was absent. No c-kit juxtamembrane domain (exon 11) or phosphotransferase domain (exon 17) mutations were found in any of the tumors examined. In conclusion, KIT protein expression is correlated with tumor grade of salivary ACC. However, gene mutation of exon 11 or exon 17 is not a mechanism of c-kit activation in these neoplasms.