Regressive changes following pretreatment of prostate cancer may represent a big challenge for the histopathologist not familiar with the assessment of pretreated specimens. Characteristic changes after antiandrogen therapy in non-malignant prostate tissue include glandular atrophy, basal cell prominence and/or basal cell hyperplasia as well as a hypercellular stroma. Morphologic changes in prostate cancer include cytoplasmic clearing and vacuolization, nuclear pyknosis and even complete cell destruction. On the glandular level, changes are characterized by various degrees of involutional changes, ranging from almost non-regressive tumor glands to complete glandular disruption with scattered isolated tumor cells dispersed in the stroma.Knowledge about these changes, the selective use of immunohistochemistry as well as a very thorough histological workup is essential for the correct assessment of these specimens.
