Clinical Characteristics and Management Challenges of Combined Small-Cell Lung Cancer: A Narrative Review

Abstract

Combined small-cell lung cancer (CSCLC) is a distinct pathological subtype of small-cell lung cancer (SCLC), in which a small-cell carcinoma component coexists with one or more non-small-cell or non-classical small-cell components, including adenocarcinoma, squamous cell carcinoma, large-cell carcinoma, or large-cell neuroendocrine carcinoma (LCNEC). This mixed histology carries direct clinical implications, as it complicates diagnosis, staging interpretation, and treatment selection. In routine clinical practice, small biopsy or cytology specimens often only capture a portion of the tumor, leading to missed or delayed identification of the combined histologic pattern. This narrative review summarizes current evidence on CSCLC, with particular focus on histopathological heterogeneity, diagnostic pitfalls, molecular reassessment, and treatment-related uncertainty. Rather than framing CSCLC as a purely molecular entity, we emphasize key issues that influence everyday clinical care: adequate tissue sampling, careful histopathological interpretation, systematic immunohistochemical work-up, selective molecular testing, and multidisciplinary treatment planning. A clearer understanding of CSCLC tumor heterogeneity may improve diagnostic accuracy and support the development of more individualized management strategies.