If the doctor punctured my wife's lung during a biopsy and never told us, do we have a case?

For there to be a viable malpractice case, you need two things:

1) Medical care that does not meet accepted standards of care--so the accidental pucture could meet this prong or criteria, so long as a "reasonable" doctor would not have done this; and

2) A physical injury or economic loss for which you could recover.

That second point is where you might have trouble. The law does not provide compensation except when there is an actual injury or loss, and the amount of compensation is directly related to the extent of injury of loss. If your wife has not been injured in any significant way--which may be the case; it seems she did not even notice--and has not incurred any additional medical costs, there is nothing to sue for; therefore, you could not recover money.