In the tumors ≤2 cm in diameter, pSTAT3 expression in the central area was higher in preinvasive tumors than in invasive tumors (p=0.005). pSTAT3 was identified in the BAC component of 88% of the EGFR mutant (n=17) and 82% of the wild-type tumors (n=33).
In summary, mixed non-mucinous bronchioloalveolar carcinoma (BAC) or papillary components and papillary predominant adenocarcinoma showed a higher frequency of EGFR mutations than mucinous BAC components; Also, EGFR mutations were significantly more common in tumors with TITF-1 or SP-A expressions than in those without (p=0.002, p=0.026), especially the sensitivity of TITF-1 (96.9%) and the negative predictive value of TITF-1 (88.2%).
From preclinical and clinical data suggesting potentially improved efficacy with a combination of an EGFR TKI and the antiangiogenic agent bevacizumab, the Southwestern Oncology Group (SWOG) initiated paired phase II trials to evaluate the combination of erlotinib/bevacizumab in patients with advanced BAC (SWOG S0635) or never smokers with advanced lung adenocarcinoma (SWOG S0636).
A multivariable analysis revealed that BAC histotype, being a never smoker, and female sex were independently associated with EGFR mutations (odds ratios: 4.542, 3.632, and 2.895, respectively).
We and others have recently demonstrated that the induction of EGFR kinase domain mutants specifically in murine lung epithelium in vivo led to development of adenocarcinoma with bronchioloalveolar carcinoma (BAC) features.
It also includes the first proposed treatment paradigm that integrates both EGFR mutational status and the sub-histologies, mucinous and nonmucinous BAC.
We assume that the LCNEC originated from the adenocarcinoma based on the fact that the patient was a non-smoking female, the tumor was located in the periphery, the tumor had a BAC component, and the same EGFR mutation was found in both the LCNEC and adenocarcinoma components.
To be never smoker (38.1%), female (25.4%), with bronchioloalveolar carcinoma (22.2%) or adenocarcinoma (15.4%) histology was associated with a higher prevalence of EGFR mutations.
As EGFR mutational frequency of atypical adenomatous hyperplasias was much lower than that of nonmucinous bronchioloalveolar carcinomas, we surmise that EGFR-mutated atypical adenomatous hyperplasias, but not atypical adenomatous hyperplasias with wild-type EGFR, are likely to progress to nonmucinous bronchioloalveolar carcinomas.
Logistic regression analysis demonstrated that female gender (odds ratio [OR], 10.913; 95% confidence interval [CI], 1.778 to 66.97; p = 0.01) and BAC, including adenocarcinomas with any bronchioloalveolar features (OR, 9.708; 95% CI, 1.464 to 64.393; p = 0.019), were significantly associated with EGFR mutations.
Detailed pathologic examination showed significant genotype-phenotype correlations between EGFR mutations and presence of a bronchioloalveolar carcinoma component, a micropapillary pattern, and the hobnail cell type.
Mutations that may predict response to adenosine 5'-triphosphate (ATP)-mimetic epidermal growth factor receptor (EGFR) inhibitors occur in the EGFR kinase domain in lung adenocarcinomas and bronchioloalveolar carcinomas (BACs).
These mutational oncogenic differences could lead to different therapeutic responses: nonmucinous BAC has been found to be sensitive to EGFR tyrosine kinase inhibitors, while mucinous BAC might be more responsive to taxane-based chemotherapy.
A significantly higher incidence of EGFR mutations was observed in bronchioloalveolar carcinomas (28%, p=0.019) and in adenocarcinomas (21%, p=0.024) than in large cell carcinomas, mixed adenocarcinomas, and NOS (4%).
EGFR TKD mutations were significantly correlated with never-smoker status (p = 0.043), absence of emphysematous or fibrotic appearance on computed tomography (p = 0.001), papillary subtype (p = 0.041), and bronchioloalveolar carcinoma features (p = 0.045).
Upon alteration of the BAC/adenocarcinoma components, the EGFR tyrosine kinase inhibitor-untreated series, which had at least one episode of an EGFR-activating mutation, represented 3 potential hypotheses: no significant EGFR evolution for a single clone, genetic alterations from mutant to wild-type EGFR for multifocal lesions, or a switch from wild-type to mutant EGFR, leading to indeterminable cancer progression.
Because EGFR mutations were detected even in most pure nonmucinous BACs, ie, lung adenocarcinoma in situ, EGFR mutation is considered a critical event in the pathogenesis of nonmucinous BAC tumors.
Two weeks after induction with doxycycline, mice that express the EGFR(L858R) allele show diffuse lung cancer highly reminiscent of human bronchioloalveolar carcinoma and later develop interspersed multifocal adenocarcinomas.