Abstract
Problem Fine needle aspiration biopsy (FNAB) is used to triage patients with salivary tumors. Distinguishing benign from malignant is difficult on cytology features and immunohistochemistry alone, leading sometimes to an incorrect surgical resection. Therefore, we evaluated whether fluorescent in situ hybridization (FISH) could be performed routinely on salivary gland tumor FNAB's, potentially to improve diagnostic accuracy. Methods Pathology files from our institution were searched for patients with salivary gland tumors. We collected data on 74 tumors: 25 benign (18 pleomorphic adenoma and 7 Warthin's tumors) and 49 malignant (miscellaneous including adenoid cystic carcinoma, mucoepidermoid carcinoma and acinic cell carcinoma, among others). Clinical presentation, staging, and follow-up information were obtained. Representative tumor blocks were disaggregated, converted to nuclear preps, and analyzed for aneuploidies of chromosomes 3, 7, 9, 11, and 19 using FISH. A novel technique creating a CMA (cytology microarray) enabled testing of multiple samples on one glass slide. Signal quantitation was performed using a Metasystems instrument. Shrunken centroid analysis was used to test for significant differences in the benign versus malignant group. Results Six tumors exhibited trisomies (8 percent); those few were exclusively limited to the malignant tumors. The tumor preps yielded adequate cellularity in 90% percent, and the CMA technique was time and cost efficient. Conclusion In a large number of salivary gland tumors, we found that chromosome copy number abnormalities do not occur with high enough frequency to enhance diagnostic accuracy. When trisomy occurs, it more likely is associated with malignancy. Significance Polyploidy seen on FISH analysis of the FNA of salivary tumors does not enhance diagnostic accuracy.
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