How do you evaluate a suspicious, but negative pleural effusion when working up NSCLC and SCLC?

Good question and this came up in my practice very recently (NSCLC). Historically, clinical trials have required 2 negative taps for entry. The patient I had in clinic appeared to have a node negative, LLL lesion with a ton of atelectasis and had a bloody tap that was negative for malignancy. It did...