Molecular testing of NSCLC using a platform for rapid detection of multiple oncogenetic mutations

IntroductionMolecular testing has become the standard of care for treatment of non–small cell lung cancer. Cytologic samples are frequently the only diagnostic material obtained due to the reduced procedure-related morbidity of fine-needle aspiration. This is a report of our laboratory’s experience using cytology specimens for molecular testing of lung tumors.Materials and methodsAll tumors were tested in the Molecular Diagnostics Laboratory at Vanderbilt University Medical Center using the ABI PRISM SNaPshot Multiplex Kit and a separate laboratory-developed test. The assay included testing for KRAS, BRAF, NRAS, PIK3CA, MEK1, AKT1, PTEN, and EGFR mutations. Specimens were tested using a paraffin-embedded cell block, and a percentage of tumor cells was determined to establish adequacy of the sample. Ten percent or more tumor cells was considered adequate. Eighty-five cytology specimens were referred for testing, and 12% were considered inadequate. Specimens tested included 55 adenocarcinomas, 6 squamous cell carcinomas, 5 large cell neuroendocrine carcinomas, 2 small cell carcinomas, and 7 categorized as non–small cell carcinoma, unable to further differentiate. Primary lung tumors as well as lung tumors metastatic to other tissues were tested. The samples ranged from 3 mm to 15 mm, and all but 1 sample had >10% tumor cells on initial and final hematoxylin and eosin slides.ResultsForty-eight mutations were identified in 42 tumors: 21 KRAS, 22 EGFR, 1 BRAF, 1 NRAS, 1 PIK3CA, 1 ERBB2, and 1 MEK1. Thirty-three tumors were negative for the mutations tested.ConclusionsThe DNA yield from cytology specimens is routinely adequate for molecular mutation analysis of lung cancer.