Histopathology of prostate carcinoma. Diagnosis and differential diagnosis.

The prognosis of prostate cancer depends largely on the degree of differentiation. Therefore the pathologist plays an important part in diagnosis and therapeutic decisions. There are three different growth patterns: glandular, cribriform, and solid-undifferentiated. In the glandular pattern, well and poorly differentiated forms are to be distinguished. Well differentiated adenocarcinomas are observed predominantly in benign nodular hyperplasia as incidental carcinomas. In case of differentiation from benign proliferations, the behaviour of the cellular nucleus--size, form, and characteristics of nucleolus--is decisive. Inflammatory stromal reaction is always absent. The growth pattern and degree of nuclear atypia determine the degree of malignancy to be demonstrated in a score. In clinically manifest carcinomas, pluriform patterns are prevailing. The lowest degree of differentiation of each case counts for the grading. In incidental carcinomas, the extension of the carcinoma has to be determined by the resection material. Here the nodular carcinoma represents a special form primarily located in the centre and obviously developing from a nodular hyperplasia. The differential diagnosis of prostatic cancer may cause great problems. Primary and secondary--postatrophic--hyperplasias may be similar to a glandular and cribriform carcinoma. Atypical hyperplasias of irregular nuclear pattern are present. Carcinoma in situ is not the proper term for such proliferations. Concerning rare types of prostate carcinomas, the urothelial carcinoma, the carcinoma with argentaffine cells, so-called endometrioid carcinomas, and squamous cell carcinomas are of importance. Following conservative, antiandrogen and radio-therapy characteristic regressive alterations can be observed in the prostate carcinoma. Response and resistance to therapy of the local tumor growth may be assessed during follow-up. A grading system is proposed for this purpose. Among all markers immunohistochemically demonstrable, only the presence of acid prostate phosphatase and prostate-specific antigen is of practical diagnostic importance in prostate cancer up to now.