Expression of KIT (CD117) in neoplasms of the head and neck: An ancillary marker for adenoid cystic carcinoma

Adenoid cystic carcinoma is an indolent salivary gland malignancy that is associated with a poor long-term prognosis. The distinction of adenoid cystic carcinoma from other head and neck neoplasms can occasionally be problematic, particularly in small biopsies. Recent studies suggest that IUT (CD 117) might be useful as an ancillary marker for adenoid cystic carcinoma; however, the expression of IUT in other benign and malignant head and neck neoplasms, including those that might mimic adenoid cystic carcinoma, has not been well studied. Here we use two different antibodies against I(IT to evaluate its expression in a series of 66 adenoid cystic carcinomas compared with its expression in 98 other neoplasms of the head and neck. Overall, 94% (n = 62) of adenoid cystic carcinomas from various anatomic sites and of various histologic subtypes were positive for at least one of the IUT antibodies, and 77% (n = 50) of adenoid cystic carcinoma cases were positive for both antibodies. This contrasted with only 8% (n = 8) of other head and neck neoplasms that were positive for both KIT antibodies (P < .001). It was of note that certain neoplasms, including pleomorphic adenoma, basal cell adenoma, polymorphous low-grade adenocarcinoma, and basal cell carcinoma, that can show histologic overlap with adenoid cystic carcinoma had significantly less IUT immunoreactivity than did adenoid cystic carcinoma (P < .001). In contrast, I(IT expression did not reliably distinguish adenoid cystic carcinoma from basal cell adenocarcinoma and basaloid squamous carcinoma (P > .05). The overall sensitivity of the two IUT antibodies for adenoid cystic carcinoma was 82-89%, and the specificity was 87-88%. The findings in this study support the potential use of IUT immunoexpression for distinguishing adenoid cystic carcinoma from many other benign and malignant head and neck neoplasms.