<s>[INST] my husbands doctor found a nodule on his lung 5 weeks ago. He had a CT scan with injection and last week a PET scan. Dr. told us today it is probably malignant but wants to do a lung biopsy. What will the biopsy show that the PET scan didn t. This has been a very long 5 weeks. Thank you [/INST] Thanks for your question on Chat Doctor. I want to ask you few questions first.1. Age of your husband. 2. Is he smoker or not? Nodule in lung needs thorough investigation.  Depending on the CT THORAX appearance, age and smoking habit, probability of malignancy can be predicted. If nodule has1. Larger size (more than 1 cm)2. Irregular margins3. Devoid of calcification4. Associated lymph nodes etc In a smoker patient with age more than 50 years, possibility of malignant nodule is high. And biopsy is needed to confirm the diagnosis of malignant nodule. Biopsy gives tissue diagnosis and if it says malignancy than it is 100% confirm diagnosis. PET scan can show positive uptake in infection, inflammation and malignancy.  So to rule out all these biopsy is needed. So go and get done biopsy. </s>