Malignant pleural mesothelioma (MPM), a rare malignancy with a poor prognosis, is mainly caused by exposure to asbestos or other organic fibers, but the underlying genetic mechanism is not fully understood. Genetic alterations and causes for multiple primary cancer development including MPM are unknown. We used whole exome sequencing to identify somatic mutations in a patient with MPM and two additional primary cancers who had no evidence of venous, arterial, lymphovascular, or perineural invasion indicating dissemination of a primary lung cancer to the pleura. We found that the MPM had R282W, a key TP53 mutation, and genome-wide allelic loss or loss of heterozygosity, a distinct genomic alteration not previously described in MPM. We identified frequent inactivating SETDB1 mutations in this patient and in 68 additional MPM patients (mutation frequency: 10%, 7/69) by targeted deep sequencing. Our observations suggest the possibility of a new genetic mechanism in the development of either MPM or multiple primary cancers. The frequent SETDB1 inactivating mutations suggest there could be new diagnostic or therapeutic options for MPM.

Abstract. Next-generation sequencing (NGS) has led to breakthroughs for genetic and genomic analyses and personalized medicine approaches for many diseases. More and more clinical laboratories are using NGS as a genetic screening tool for providing mutation information that is used to select the best treatment regimens for cancer patients. However, several obstacles prevent the routine implementation of NGS technology into the clinical molecular diagnosis setting: the sophisticated sample preparation process, high cost, timeconsuming data analyses, as well as the reproducibility and accuracy of interpretation. To systematically evaluate the performance and quality of targeted NGS cancer panel analyses in clinical laboratories, we performed three different tests: i) laboratory-to-laboratory accuracy test, ii) intra-laboratory precision validation, and iii) limit of detection test, using formalin-fixed, paraffin-embedded cancer tissue specimens, cell lines and mutation positive DNA. A laboratory-to-laboratory accuracy test performed using 51 samples showed 100% sensitivity and 99.97% specificity. For the intra-laboratory precision test, 100% reproducibility was observed. For the limit of detection test, KRAS mutations from samples diluted from 70 to 2% of mutant allele frequencies were detected correctly. We believe that the present study demonstrated the feasibility of clinical implementation of a targeted NGS cancer panel analysis for personalized medicine.