Small cell lung carcinoma metastatic to the stomach: Commonly overlooked, limited treatment options

Abstract

Small cell lung carcinoma metastatic to the stomach, whether synchronous or metachronous, is a rare phenomenon accounting for < 0.5% of lung cancers. Hence it can be overlooked by clinicians resulting in delayed diagnosis. This manuscript comments on Yang et al’s article which reported 3 such cases. The main diagnostic features are based on routine morphology comprised of small cells with hyperchromatic nuclei, scant cytoplasm, brisk mitoses and necrosis. This can be supplemented by immunohistochemistry demonstrating positivity for cytokeratin, thyroid transcription factor-1 and neuroendocrine markers as well as a high Ki-67 labelling index. Imaging modalities such as positron emission tomography/contrast computed tomography help to confirm lung origin and rule out the possibility of extra-pulmonary small cell carcinoma. The predominant mechanism of spread is most likely hematogeneous. Prognosis is generally poor since this represents stage 4 disease but survival can be improved by chemo/radiotherapy and palliative surgery in select cases. Though outcomes have not changed much in the last several decades, the recent Food and Drug Administration approval of immune checkpoint inhibitors was a significant milestone as was the delineation of small cell lung carcinoma molecular subtypes. Liquid biopsies are increasingly being used for biomarker studies in clinical trials to assess treatment response and prognosis.

Keywords: Gastric metastasis; Small cell lung carcinoma; Histopathology; Immunohistochemistry; Positron emission tomography/contrast computed tomography; Chemoradiotherapy; Immunotherapy; Surgery; Biomarkers; Clinical trials

Core Tip: Small cell lung carcinoma metastatic to the stomach is rare and can thus be overlooked. Diagnosis requires conventional morphology supplemented by immunohistochemistry as well as appropriate imaging modalities. While outcomes are generally poor, palliative chemo/radiotherapy with surgery in select cases can improve survival and quality of life. The recent Food and Drug Administration approval of immune checkpoint inhibitors was a significant milestone as was the delineation of small cell lung carcinoma molecular subtypes. Liquid biopsies and biomarkers are increasingly being used in clinical trials for therapeutic stratification and prognostication.