Question

What are solitary pulmonary nodules (SPNs)?

Hint:

Size, growth rate, and the presence of risk factors such as smoking history are important factors in assessing the risk of malignancy in solitary pulmonary nodules (SPNs).

Answer 1

A solitary pulmonary nodule (SPN) is a discrete, well-defined round or oval lesion in the lung, usually less than 3 cm in size, which is surrounded by normal lung parenchyma. SPNs are often found incidentally on chest radiographs or CT scans and can be benign or malignant.
Step 1: Characteristics of SPNs:
- SPNs are typically asymptomatic, and the majority are discovered incidentally during imaging for other reasons.
- The size of the nodule, its growth rate, and the patient's risk factors (e.g., smoking history, age, previous cancer) are critical in determining the likelihood of malignancy.
Step 2: Differential Diagnosis:
1. Benign Causes: Most SPNs are benign and may be due to infectious granulomas (e.g., tuberculosis), hamartomas, or inflammatory lesions.
2. Malignant Causes: Malignant SPNs are most commonly due to primary lung cancer (e.g., non-small cell lung cancer), metastatic tumors, or lymphoma. The risk of malignancy increases with the size of the nodule, age of the patient, and smoking history.
Step 3: Evaluation of SPNs:
- The initial evaluation of an SPN includes a detailed history, clinical examination, and imaging studies. A contrast-enhanced chest CT is typically performed to assess the size, location, and characteristics of the nodule (e.g., spiculated edges, calcification pattern).
- If the nodule is suspicious for malignancy, further investigation may include biopsy (e.g., CT-guided needle biopsy) or positron emission tomography (PET) scan.