ABSTRACT
The majority of prostate cancers develop initially in the peripheral zone of the prostate, either from, or in conjunction with, prostatic epithelium neoplasia. They generally grow slowly at first, often with a cell-doubling time of more than 2 years. As dedifferentiation occurs due to sequential mutations, however, clonal selection results in an increase in the rate of cell division and the development of local invasion. The TNM (tumors/nodes/metastases) staging system classifies prostate cancers locally as T1-4 (Figure 51). Impalpable tumors, which are now being detected with increasing frequency, are classified as T1A and T1B (according to grade and volume) when identified by transurethral resection (TUR), or as T1C if impalpable, and detected purely on the basis of an elevated PSA and subsequent transrectal ultrasound (TRUS)-guided biopsy. If the cancer is well differentiated and involves less than 5% of the resected material, it is classed as a T1A and carries a good prognosis. If, on the other hand, the lesion is moderately or poorly differentiated and involves more than 5% of the resected chippings, then it is termed a T1B lesion. These lesions are associated with a poorer prognosis and a higher probability that residual cancer will persist in the prostate remnant after resection and require further therapy. Local extension of prostate adenocarcinoma most frequently occurs through the prostatic capsule (so-called capsular extension) posterolaterally via perineural or lymphatic channels, which follow the prostatic branches of the neurovascular bundles of Walsh (Figures 52 and 53). For this reason, it is advised that, during a nerve-sparing radical retropubic prostatectomy, the neurovascular bundle on the affected side be sacrificed to reduce the chances of a positive margin in that location. Further local extension most commonly involves the seminal vesicles, a pathological finding which is associated with a poor prognosis. Prostatic tumor may also directly infiltrate the bladder base and obstruct the ureteric orifices, producing hydronephrosis and, if bilateral, eventual anuria. The ureters may also be obstructed by involved lymph nodes, usually at the level of the pelvic brim. Posterior extension of the tumor is less common, as Denonvillier’s fascia appears to act as an effective barrier to spread. Occasionally, however, prostatic adenocarcinoma may encircle the rectum and obstruct the lower bowel (Figure 54).
