Prevalence and malignancy risk of incidental pulmonary nodules: insights from a retrospective study in Saudi Arabia

Background: Incidental pulmonary nodules (IPNs) are frequently identified in computed tomography (CT) scans performed for unrelated clinical indications. While most are benign, some harbor malignancy, necessitating proper evaluation. This study assesses the prevalence, characteristics, and malignancy predictors of IPNs. Methods: A retrospective review of CT scans conducted between January 2015 and December 2022 at a single institution was performed. From 16,433 CT reports, 749 cases of pulmonary nodules were identified, of which 219 met inclusion criteria. Of 219 incidental nodules identified, 103 (47%) had follow-up CT imaging and comprised the analytic cohort for outcome assessment. Demographic and clinical data, including smoking history and nodule characteristics, were analyzed. Malignancy was confirmed through histopathological examination. Statistical analyses included descriptive comparisons and penalized logistic regression to account for low event rates. Results: The study involved 219 patients with an equal sex distribution. The median nodule count was 5 per patient, with a median size of 5 mm. Most nodules were in the right upper lobe. Malignancy was detected in 5 of 103 patients with follow-up imaging (4.85%), which is significantly higher compared with national registry data of the general population. While malignant nodules exhibited slightly larger median sizes (6.5 mm), they did not significantly differ from benign ones in terms of size distribution or lobar location (P>0.05). Patients above 50 years old showed a significantly higher number of nodules (P=0.002). Conclusions: A significant proportion of IPNs in this cohort demonstrated malignancy risk, highlighting important gaps in follow-up and documentation in routine clinical practice. These findings highlight the need for structured, risk-based follow-up protocols to ensure timely evaluation while avoiding unnecessary interventions.