Detailed research on prostate anatomy was also carried out and McNeal proposed that the prostate was composed of three distinct glandular zones, namely transitional zone, peripheral zone and central zone (McNeal, 1968). The clinical relevance became important considering that the majority (70-80%) of cancers arise in the peripheral zone. The findings of research into ultrasound appearances of prostate cancer confirmed varying characteristics and early stage lesions were seen to be indistinct from normal prostatic tissue, indicating that TRUS as a diagnostic tool lacked specificity and had limitations. With the widespread use of serum PSA testing came the detection of early stage, low volume cancers that did not necessarily.
