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KRAS is the most frequently mutated oncogene in non-small cell lung cancers (NSCLC), with a frequency of around 30%, and encoding a GTPAse that cycles between active form (GTP-bound) to inactive form (GDP-bound). The KRAS mutations favor the active form with inhibition of GTPAse activity. KRAS mutations are often with poor response of EGFR targeted therapies. KRAS mutations are good predictive factor for immunotherapy. The lack of success with direct targeting of KRAS proteins, downstream inhibition of KRAS effector pathways, and other strategies contributed to a focus on developing mutation-specific KRAS inhibitors. KRAS p.G12C mutation is one of the most frequent KRAS mutation in NSCLC, especially in current and former smokers (over 40%), which occurs among approximately 12–14% of NSCLC tumors. The mutated cysteine resides next to a pocket (P2) of the switch II region, and P2 is present only in the inactive GDP-bound KRAS. Small molecules such as sotorasib are now the first targeted drugs for KRAS G12C mutation, preventing conversion of the mutant protein to GTP-bound active state. Little is known about primary or acquired resistance. Acquired resistance does occur and may be due to genetic alterations in the nucleotide exchange function or adaptative mechanisms in either downstream pathways or in newly expressed KRAS G12C mutation.

Non-small cell lung cancer (NSCLC) is the most common cancer in the world. Activating epidermal growth factor receptor (EGFR) gene mutations are a positive predictive factor for EGFR tyrosine kinase inhibitors (TKIs). For common EGFR mutations (Del19, L858R), the standard first-line treatment is actually third-generation TKI, osimertinib. In the case of first-line treatment by first (erlotinib, gefitinib)- or second-generation (afatinib) TKIs, osimertinib is approved in second-line treatment for patients with T790M EGFR mutation. Despite the excellent disease control results with EGFR TKIs, acquired resistance inevitably occurs and remains a biological challenge. This leads to the discovery of novel biomarkers and possible drug targets, which vary among the generation/line of EGFR TKIs. Besides EGFR second/third mutations, alternative mechanisms could be involved, such as gene amplification or gene fusion, which could be detected by different molecular techniques on different types of biological samples. Histological transformation is another mechanism of resistance with some biological predictive factors that needs tumor biopsy. The place of liquid biopsy also depends on the generation/line of EGFR TKIs and should be a good candidate for molecular monitoring. This article is based on the literature and proposes actual and future directions in clinical and translational research.

OBJECTIVES Epidermal growth factor receptor (mEGFR) and v-Ki-ras2 Kirsten rat sarcoma viral oncogen homologue (mKRAS) mutations are the two main oncogenic drivers in resected non-small-cell lung cancer (NSCLC). We aimed to evaluate the correlation between histopathological prognostic factors and these mutations in resected NSCLC. METHODS We retrospectively reviewed data from 841 patients who underwent a surgical resection with a curative intent for NSCLC between 2007 and 2012. RESULTS KRAS mutations were observed in 255 patients (32%) and mEGFR in 103 patients (12%). A correlation was observed between mKRAS patients and lymph node involvement [Cramer's V: 0.451, P < 0.001, OR: 7.5 (95% CI: 5.3-10.7), P < 0.001]. Otherwise, a correlation was observed between mKRAS and the risk of harbouring 2 N2 stations [Cramer's V: 0.235, P = 0.02, OR: 3.04 (95% CI: 1.5-6.3), P = 0.004]. High lymph node ratio and angioinvasion were also significantly more frequent in mKRAS [Cramer's V: 0.373, P < 0.001, OR: 6.37 (95% CI: 3.9-10.5), P < 0.001; and Cramer's V: 0.269, P < 0.001, OR: 3.25 (95% CI: 2.4-4.4), P < 0.001, respectively]. Skip N2 and microscopic N2 were significantly more frequent in mEGFR [Cramer's V: 0.459, P < 0.001, OR: 18 (95% CI: 5.6-57.8), P < 0.001; and (Cramer's V: 0.45, P < 0.001 OR: 21.14 (95% CI: 9.2-48.3), P < 0.001, respectively]. CONCLUSIONS We observed a correlation between mKRAS and negative histopathological prognostic factors and between mEGFR and positive prognostic factors. One can wonder whether histopathological prognostic factors are only clinical reflections of molecular alterations.

Aggressive fibromatosis (AF) or desmoid tumor is a rare condition, characterized by deep tissue invasion by a monoclonal fibroblastic neoplasm, developed from musculoaponeurotic structures. Surgery is the treatment of choice, but negative margins can hardly been achieved in large tumors, and can lead to major functional disability. AF medical therapy includes nonsteroids anti-inflammatory drugs, tamoxifen, with inconsistent results. Several reports of imatinib efficacy in AF appear in the literature. Here, we describe for the first time a V530IKITexon 10 mutant that was associated to a dramatic imatinib response in an extraabdominal aggressive fibromatosis. The previously discovered V530I substitution was characterized in the core binding factor AML, but had never been reported in any other condition, so far. In this paper, we discuss theKITexon 10 mutations or polymorphisms that have been described in a variety of KIT-related conditions, including acute myelogenous leukemia, mastocytosis, and aggressive fibromatosis.