Conflicting info one doc says small cell lung cancer cannot be ruled out by unremarkable chest ct scan. another doc says it can as sclc is exceptionally unlikely with nothing significant on ct. any radiologists here have any views. thank you.

No conflict there: With any tumor, any solid cancer, using an imaging method such as plain x-ray, CT, US, or MRI always means there is a minimum size of tumor below which you cannot see the tiny tumor. Realize that tumors likely start as 1 "invisible" cell, then 2 cells, then 4, then 8, then 16... eventually visible to some imaging machine. Nobody can say for sure he does not have a tumor that is too small to see.