No pleural mass in chest ct scan,clear pleural exudate (lab results say it is exudate not transudate).no fever or cough. can we rule out lung cancer?

Not enough info....: With the information provided, lung cancer cannot be ruled out. Need to know if any mass or abnormality was seen on the chest CT scan. An exudative pleural effusion could be due to many things including pneumonia, cancer, etc. A sample of the fluid should be sent for a variety of cultures as well as looked at for malignant cells. More testing is definitely needed for a diagnosis to be made!

Lung Cancer unlikely: In a 30 year old, Lung cancer is not a likely cause of pleural effusion. Depending on other test results and symptoms(?any Fever), TB is one diagnosis high on the list. Your doctor should do further testing for TB and you may need emiric Anti-TB treatment if your fluid keeps reaccumulating or if you have fever on an ongoing basis and if there is significant weight loss. ESR is a useful test to do.