MICROSATELLITE ALTERATIONS AT CHROMOSOME 8Q LOCI IN PLEOMORPHIC ADENOMA

OBJECTIVE: To determine the extent, localization, and clinical signifi cance of microsatellite loci alterations at sites of reported cytogene tic abnormalities in pleomorphic adenomas. BACKGROUND: Pleomorphic ade noma is a benign salivary gland tumor with a propensity for recurrence and potential for malignant conversion. Although its cause remains un clear, clonal cytogenetic abnormalities have been reported consistentl y. DESIGN: DNA extracted from paired normal and tumor tissue specimens from 1 patient with carcinoma ex pleomorphic adenoma and 17 patients with pleomorphic adenoma (3 contained foci of carcinoma ex pleomorphic adenoma) was evaluated for loss of heterozygosity at microsatellite l oci with a multiplex polymerase chain reaction-based analysis. Correla tion with clinical and pathologic features was performed. RESULTS: Ove rall 10 (56%) of 18 cases manifested loss of heterozygosity at the loc i tested. The frequency of loss of heterozygosity noted on 3p, 6q, 8p, 8q, and 12q microsatellite loci was 17%, 12%, 8%, 47%, and 27% of inf ormative cases, respectively. Specimens from patients with carcinoma e x pleomorphic adenoma showed a similar loss of heterozygosity incidenc e at these loci. No apparent association between molecular abnormaliti es and clinical-pathologic features was observed in this cohort. CONCL USIONS: Loss of heterozygosity at microsatellite loci on 8q, a breakpo int at which translocations have been previously documented in pleomor phic adenoma, is a frequent event in this tumor. The incidence is not increased in patients with focal carcinoma ex pleomorphic adenoma, sug gesting that loss of heterozygosity at 8q is an early event in tumorig enesis. Further evaluation at these loci is needed to identify potenti al tumor suppressor genes that may be associated with the initiation a nd progression of pleomorphic adenomas.