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Introduction: Differentiation between intrapulmonary metastasis (IPM) and multiple primary lung cancers (MPLC) in patients with synchronous or metachronous lung tumor nodules is critical but challenging., Objective: We proposed an algorithm to evaluate clonal origin based on trunk (initiating) versus branching drivers and the prevalence of mutations in lung adenocarcinomas., Methods: Driver mutations were examined using next-generation sequencing in five trunk driver genes (BRAF, EGFR, ERBB2, KRAS, and NRAS) and three branching driver genes (ATK1, PIK3CA, and TP53)., Results: Mutational profiling supported same clonality and likely same clonality, respectively, in 39 and 14 of 66 pairs of specimens with known identical clonal origin. Discordance of TP53 mutations (branching drivers) was observed in three pairs. Subsequent analyses of 30 pairs of synchronous or metachronous lung tumor nodules revealed different clonality and likely different clonality in 17 and 2 pairs, respectively, including three pairs with similar histomorphology; same clonality and likely same clonality in three and five pairs, respectively, including two pairs with different histomorphology; and inconclusive or noninformative results in three pairs., Conclusion: While discordance of trunk drivers indicated MPLC in patients with synchronous or metachronous lung tumor nodules, discordance of branching drivers did not exclude IPM. Concordance of uncommon drivers supported IPM, whereas concordance of common drivers did not exclude MPLC. Additional recommendations from official organizations are needed to guide applications of molecular markers in defining clonality of multiple lung tumor nodules.

Background: Selective IDH1 and IDH2 inhibitors have been approved for targeted therapy of acute myeloid leukemia. Clinical trials for solid tumors with IDH1 and IDH2 (IDH1/2) mutations are ongoing. Reports of IDH1/2-mutated non-small cell lung cancers (NSCLCs), however, are limited., Methods: We evaluated IDH1/2 mutations in 1,924 NSCLC specimens (92% adenocarcinoma) using a next-generation sequencing assay., Results: Retrospective quality assessments identified false detection of IDH1 c.395G>A (p.R132H) resulting from cytosine deamination (C:G→T:A) artifact in one specimen. IDH1/2 mutations were detected in 9 (0.5%) adenocarcinomas taken by fine-needle aspiration (n = 3), thoracentesis (n = 2) or core biopsy (n = 4). All nine adenocarcinomas showed high-grade features. Extensive clear cell change, however, was not observed. High expression (50% or greater) of PD-L1 was observed in two of five specimens examined. IDH1/2 mutations were associated with old age, smoking history, and coexisting KRAS mutation. Lower than expected variant allele frequency of IDH1/2 mutants and coexistence of IDH1/2 mutations with known trunk drivers in the BRAF, EGFR, and KRAS genes suggest they could be branching drivers leading to subclonal evolution in lung adenocarcinomas. Multiregional analysis of an adenocarcinoma harboring two IDH2 mutations revealed parallel evolution originating from a KRAS-mutated lineage, further supporting subclonal evolution promoted by IDH1/2 mutations., Conclusions: IDH1/2 mutations in NSCLCs are uncommon. They occur in adenocarcinomas with high-grade features and may be branching drivers leading to subclonal evolution. Accumulation of more IDH1/2-mutated NSCLCs is needed to clarify their clinicopathological characteristics and implications for targeted therapy., (© 2020 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.)

EGFR-mutated lung adenocarcinomas routinely develop resistance to tyrosine kinase inhibitors (TKI). To better characterize the relative frequencies of the resistance mechanisms, we analyzed 48 EGFR-mutated TKI-resistant specimens from 41 patients. Next-generation sequencing of post-treatment specimens detected EGFR p.T790M in 31 (79%) of 39 patients, PIK3CA mutations in 10 (26%), EGFR p.S768_V769delinsIL in one, and KRAS p.G12C in one. Five PIK3CA mutations were outside of codons 542, 545, and 1047. Three of four pre-treatment specimens did not carry the PIK3CA mutation found in the post-treatment sample. Small cell carcinoma transformation was identified in four patients; none had p.T790M, including two where p.T790M was identified in the co-existing adenocarcinoma. In p.T790M-mutated specimens, the allele frequency was less than 5% in 24% of cases. p.T790M allele frequency was usually lower than that of the sensitizing mutation indicating that the resistance mutation was present either in a subset of cells or, if the sensitizing mutation was amplified, in a subset of the sensitizing alleles of a dominant clone. Eight patients had multiple resistance mutations, suggesting either multiple separate resistant clones or a single clone harboring multiple resistance mechanisms. PIK3CA mutations appear to be a more significant resistance mechanism than previously recognized., Competing Interests: The authors declare no conflicts of interest.

Heterotopic pancreatic parenchyma recapitulates the normal pancreas in extrapancreatic locations and, on rare occasions, can even give rise to pancreatic adenocarcinoma. The genetic signatures of pancreatic adenocarcinoma and its precursor lesions are well characterized. We explored the genetic alterations in precursor lesions (intraductal papillary mucinous neoplasms [IPMN], pancreatic intraepithelial neoplasia [PanIN]) in patients with pancreatic heterotopias but without concomitant pancreatic ductal adenocarcinomas. This allowed us to determine whether the stereotypical dysplasia--infiltrating carcinoma sequence also occurs in these extrapancreatic foci. Seven cases of heterotopic pancreas with ductal precursor lesions were identified. These included 2 IPMNs with focal high-grade dysplasia and 5 PanINs with low- to moderate-grade dysplasia (PanIN grades 1-2). Neoplastic epithelium was microdissected and genomic DNA was extracted. Sequencing of commonly mutated hotspots (KRAS, TP53, CDKN2A, SMAD4, BRAF, and GNAS) in pancreatic ductal adenocarcinoma and its precursor lesions was performed. Both IPMNs were found to have KRAS codon 12 mutations. The identification of KRAS mutations suggests a genetic pathway shared with IPMN of the pancreas. No mutations were identified in our heterotopic PanINs. One of the possible mechanisms for the development of dysplasia in these lesions is field effect. At the time of these resections, there was no clinical or pathologic evidence of a prior or concomitant pancreatic lesion. However, a clinically undetectable lesion is theoretically possible. Therefore, although a field effect cannot be excluded, there was no evidence for it in this study.

Objectives: To propose an operating procedure for validation of discordant trunk driver mutations.Methods: Concordance of trunk drivers was examined by next-generation sequencing in 15 patients with two to three metastatic lung cancers and 32 paired primary and metastatic lung cancers.Results: Tissue identity was confirmed by genotyping 17 single-nucleotide polymorphisms within the panel. All except three pairs showed concordant trunk drivers. Quality assessment conducted in three primary and metastatic pairs with discordant trunk drivers indicates metastasis from a synchronous or remote lung primary in two patients. Review of literature revealed high discordant rates of EGFR and KRAS mutations, especially when Sanger sequencing was applied to examine primary and lymph node metastatic tumors.Conclusions: Trunk driver mutations are highly concordant in primary and metastatic tumors. Discordance of trunk drivers, once confirmed, may suggest a second primary cancer. Guidelines are recommended to establish standard operating procedures for validation of discordant trunk drivers. [ABSTRACT FROM AUTHOR]