Lung Cancer in Non-Smokers: Integrating Histopathological Patterns, Molecular Profiles and Therapeutic Strategies

Abstract

Non-smoker lung cancer represents a distinctive clinical and pathological entity, comprising 10-25 percent of all lung cancer cases globally. It possesses a unique epidemiology, histopathology, and molecular profile that fundamentally diverges from smoking-related diseases. This narrative literature review meticulously examines the specific histopathological characteristics that delineate this significant subset of lung cancer patients. Our systematic review of published studies reveals that Non-smokers predominantly present with well-differentiated adenocarcinoma (85-90% vs. 40-50% in smokers) and exhibit characteristic morphological patterns, including lepidic growth, acinar architectures, and papillary patterns that closely align with unique molecular drivers. Immunohistochemical analyses indicate a more than twofold increase in TTF-1 expression among Non-smokers (80-90% vs. 60-70%), alongside a twofold higher prevalence of Napsin A in comparison to smokers (85-95% vs. 70-80%). Furthermore, targetable oncogenic drivers are significantly enriched through molecular profiling, with EGFR mutations occurring in 40-50% of cases compared to 10-15% in smokers, and ALK rearrangements identified in 5-10% versus rare occurrences in smokers; ROS1 fusions further contribute to this profile. The confluence of morphological patterns, immunohistochemical profiles, and molecular alterations carries substantial diagnostic and therapeutic implications, as histological characteristics may foreshadow molecular status and guide the selection of targeted treatments within this population. The future of optimizing diagnosis and treatment for Non-smokers with lung cancer is poised to benefit from emerging technologies such as liquid biopsy and AI-enabled pathology, alongside historically agnostic therapeutic strategies that focus on targeting specific molecular drivers independently of current morphological subtypes. This review encapsulates recent evidence underscoring the critical necessity for integrated morphological, immunohistochemical, and molecular analyses to facilitate accurate diagnoses, formulate appropriate molecular testing strategies, and make effective therapeutic decisions for Non-smoker lung cancer patients.