Non-diagnostic means that a diagnosis could not be made from the tissue sample provided by your doctor. This can happen when the tissue sample is too small, is damaged during retrieval or processing, or because the cells in the sample were no longer alive at the time the sample was received in the lab. Your pathologist may also use this result when the type of tissue seen under the microscope is different from the tissue your doctor was trying to sample.
Non-diagnostic does not mean normal and your doctor should not interpret this result as a final diagnosis. If the tissue sample was removed to look for cancer or another serious medical condition, your doctor should consider performing a second procedure to provide the pathologist with more tissue to examine under the microscope.