Testicular biopsy is surgery to remove a piece of tissue from the testicles and examined it under a microscope. The test is most often done to find the cause of male infertility. It is done when a semen analysis suggests that there is abnormal sperm and other tests have not found the cause. Two types of outcomes from the testicular biopsy are possible: 1) Sperm development appears normal. No cancerous cells are found; 2) Abnormal results in terms of sperm count, morphology, or motility may mean a problem with sperm or hormone function. A biopsy may be able to find the cause of the problem. In some cases, sperm obtained from a testicular biopsy can be used for in vitro fertilization.