[Undiagnosed microinvasive carcinomas of the prostate].

Quality assurance is becoming increasingly important in all aspects of health care, but a growing workload in recent years may delay the introduction of new quality assurance procedures. In 1994-95, in order to evaluate the standard of quality in executing routine histopathological procedures, a total of 1,135 prostatic specimens representing all surgical material taken from the prostate during 1974-75 were reviewed. The patients were followed up for to 20 years by comparing with the files of The Norwegian Cancer Registry. Only a few registration errors were found. Microscopic examination in 1994-95 revealed 311 carcinomas, 83 of which were not recorded in 1974-75. 73 of the patients had not received treatment. The histology reports revealed suspected malignancy, with irregular or atypical epithelium, or both, in 42% of the 83 carcinomas not reported in 1994-95, whereas for 45 carcinomas the histology reports did not describe changes suggestive of malignancy. Only 3% of the patients not treated died of prostate cancer during the follow-up time, compared with 78 (54%) cancer deaths in the group that had received treatment. Most undiagnosed cancers were well differentiated and in the pT1a category. It is important that the clinician is aware of the fairly benign outcome of these borderline tumors in order to avoid overtreatment.