Which pulmonary nodule could be a sign of systemic disease in children?

<bold>Introduction:</bold> We aimed to evaluate the clinical and radiological features of patients with pulmonary nodule (PN) and their diagnoses after detecting PN. <bold>Materials and Methods:</bold> Age, gender, systemic diseases, clinical and radiological findings, diagnoses after detecting PN were recorded for the patients with PN in 2007-2023. <bold>Results:</bold> There were a total of 206 patients, 54.9% were male. The current age of the patients was 14.9(0.3-28), age of imaging was 9.3(0.2-18) years. The follow-up period was 51.5(1-209) months. In 33% of patients, PN was detected on imaging due to respiratory symptoms, 21.8% were incidental. PN was detected in 45.1% on imaging due to underlying systemic disease;the most common was haematology-oncological disease(19.9%). The most common symptom was cough (25.7%). The median number of PN was 2(1-16), the size was 3(0,5-18)mm. PN was most frequently located bilaterally(41.3%), parenchymally(55.3%). The most common finding accompanying PN on imaging was lymphadonopathy(32.5%).PN was nonspecific in 66% of patients. In 23,3% of patients had a new diagnoses after PN;malignancy in 29.2%, rheumatological disease in 16.7%, fungal infection in 14.6%, COVID-19 in 8.3%, bronchiolitis obliterans in 8.3%, tuberculosis in 6.3%. In those with new diagnoses after detecting PN, the patient age was younger, the number of PN was higher, the largest PN size of 5mm or larger, ground glass, cavitation and vascular relationship were higher and they were bilateral and more parenchymal localised (p<0.05). Discussion:If the number of PN is high, the size is more than 5mm or larger, there are additional radiological findings accompanying the nodule, bilateral and parenchymal localisation, it may be a sign of a systemic disease.