| Category | Description | 
 | Benign Causes | 
Granulomas: Most commonly infections e.g. TB or histoplasmosis. Often calcified.Hamartomas: Benign tumours that typically contain cartilage, fat, and connective tissue. Most common benign tumours of the lung.Infectious Nodules: Bacteria, fungi, or parasites. History of recent or past infections.Inflammatory Nodules: Conditions like RA/Wegener's granulomatosis, causing localized inflammation in the lungs.Vascular Lesions: AVM or pulmonary infarcts, which may appear as nodules. | 
 | Malignant Causes | 
Primary Lung Cancer: The most concerning cause of an SPN, especially in older smoker. Adenocarcinoma is commonest.Metastatic Tumours: Secondary cancer from breast, colon, or kidney.Carcinoid Tumours: Neuroendocrine tumours can appear as solitary nodules and malignant. | 
 | Management | 
 | Initial Evaluation | 
Review of Imaging: Evaluate prior chest imaging to assess the stability of the nodule over time. Static Nodules for 2 years are likely benign.Risk Assessment: Consider age, smoking history, size, and characteristics of the nodule (e.g., size, shape, calcification). | 
 | Low-Risk Nodules | 
Serial Imaging: CT scans at intervals (e.g., 3, 6, 12, and 24 months) to monitor for changes in size or appearance.Observation: Many benign nodules can be safely monitored without invasive procedures if they remain stable over time. | 
 | Intermediate-Risk Nodules | 
Further Imaging: PET-CT scan to assess metabolic activity. Highly active nodules may warrant biopsy.Biopsy: Consider transthoracic needle biopsy or bronchoscopy, depending on the anatomy and access and size. | 
 | High-Risk Nodules | 
Surgical Resection: If a nodule is highly suspicious for malignancy, especially in high-risk patients, surgical removal (lobectomy, segmentectomy) is often recommended.Video-Assisted Thoracoscopic Surgery (VATS): A minimally invasive surgical option to obtain a biopsy or remove the nodule. | 
 | Post-Treatment Follow-Up | 
Ongoing Surveillance: Regular follow-up imaging to monitor for recurrence or the development of new nodules, particularly in patients with a history of malignancy.Oncologic Consultation: For malignant nodules, multidisciplinary management including oncology, pulmonology, and thoracic surgery may be necessary. |