Epidemiology of typical and atypical lung neuroendocrine tumors in a rural U.S. population.

e22631 Background: Lung neuroendocrine neoplasms comprise a heterogeneous group of tumors that include typical and atypical carcinoid tumors. These well-differentiated, low-grade malignancies are most diagnosed in the fifth to sixth decades of life, with atypical carcinoids often presenting 5-10 years later. Although prior studies have described demographic patterns, associations such as biological sex remains incompletely characterized, and data from rural populations are limited. We aimed to characterize sex-based and epidemiologic differences between typical and atypical lung neuroendocrine tumors in a rural U.S. population. In this rural cohort, lung neuroendocrine tumors demonstrated distinct sex-based patterns by histologic subtype, warranting validation in larger studies. Methods: This retrospective cohort study reviewed adult patients treated at Renown Regional Medical Center in Nevada between Jan 2020-Dec 2025 with a pathology-confirmed diagnosis of primary pulmonary typical or atypical lung carcinoid tumor. Demographic variables and clinical characteristics were collected under IRB approval. Descriptive statistics like Fisher’s exact test and Wilcoxon Rank-Sum were utilized to summarize the cohort. Results: A total of 43 patients were identified with typical or atypical lung carcinoids. Of the total patients, 35 (81%) had typical lung carcinoids, and 32 (74%) were female. 5 (11%) had an autoimmune disease all of which were females with typical carcinoid tumors, whereas no cases of autoimmune disease were observed among patients with atypical carcinoids. Of the atypical patients, 5 (63%) of the patients were male. Female sex was more common among patients with typical compared with atypical carcinoids (81% vs 38%; p = 0.02). The median age for typical carcinoids was higher (64.5 years) compared to atypical (50.5 years), though not statically significant (p = 0.10). Typical carcinoids occurred predominantly among White, non-Hispanic patients (31/34, 91%), whereas atypical tumors were more evenly distributed across racial and ethnic groups, though subgroup sizes were small. Conclusions: In a rural northern Nevada cohort, females comprised a higher proportion of patients with pulmonary neuroendocrine carcinoid tumors, suggesting a possible regional association. In addition, sex distribution differed by histologic subtype, with female predominance in typical and male predominance in atypical tumors. Although no established association between autoimmune disease and pulmonary carcinoid tumors exists, the clustering of autoimmune conditions among female patients with typical carcinoids in this cohort represents a hypothesis-generating observation that warrants further investigation. Future studies should evaluate whether this apparent female predominance persists across broader rural populations and explore potential environmental or biologic contributors.