Morphological changes in prostatic adenomas after transurethral microwave thermotherapy

Objective To study the extension and type of tissue damage in prostatic adenomas after transurethral microwave thermotherapy (TUMT). Patients and methods Seven patients with benign prostatic hyperplasia and scheduled for open adenectomy underwent TUMT before surgery. TUMT was performed 2 h before operation in one patient, 24 h before in five and one week before in the remaining patient. The excised adenomas were examined by routine light microscopy. In addition, the terminal deoxynucleotidyl nick-end labelling (TUNEL) technique was used to search for DNA-strand breaks in areas with morphological alterations suggestive of apoptosis. Due to technical problems, TUMT was inadequate for one patient, i.e. the effect given was extremely low. Results In six cases, histopathological changes were found in limited areas extending from the urethra for 20-25 mm into the prostatic tissue. The predominant histopathological findings were areas of necrosis surrounded by cells with apoptotic features. The latter proved to be TUNEL-positive, i.e. they contained nuclei with DNA fragmentation of the apoptotic type. In the case with inadequate TUMT, there was no heat-induced tissue damage. Conclusion The area of tissue damage seen after TUMT was relatively small compared with the volume of the prostates. The main histopathological finding was massive necrosis, but cells undergoing apoptosis were also identified. Obviously, temperatures lower than those leading to necrosis induced apoptosis, which is a discrete type of cell death not associated with oedema or inflammatory reaction.