How Is Peyronie's Disease Diagnosed?
First, your doctor will talk to you and ask about any circumstances, such as injury, that may have occurred prior to symptoms appearing. Your doctor can feel the hardened tissue caused by the disease during an exam, although sometimes it is necessary to do the exam with the penis erect. In some cases where the doctor's exam does not confirm Peyronie's disease, or in cases where the condition develops rapidly, your doctor may perform a biopsy. A biopsy involves removing tissue from the affected area to be examined in a lab.
Source: http://www.webmd.com