Pathology The noninvasive proliferation of epithelial cells within ducts is termed prostatic intraepithelial neoplasia. PIN is a precursor of cancer, but not all PIN lesions develop into invasive cancers. Of the cancers identified, 95% are adenocarcinomas; the remainder are squamous or transitional cell tumors or, rarely, carcinosarcomas. Metastases to the prostate are rare, but in some cases colon cancers or transitional cell tumors of the bladder invade the gland by direct extension. When prostate cancer is diagnosed, a measure of histologic aggressiveness is assigned using the Gleason grading system, in which the dominant and secondary glandular histologic patterns are scored. | Chapter 091. Benign and Malignant Diseases of the Prostate Part 4 Pathology The noninvasive proliferation of epithelial cells within ducts is termed prostatic intraepithelial neoplasia. PIN is a precursor of cancer but not all PIN lesions develop into invasive cancers. Of the cancers identified 95 are adenocarcinomas the remainder are squamous or transitional cell tumors or rarely carcinosarcomas. Metastases to the prostate are rare but in some cases colon cancers or transitional cell tumors of the bladder invade the gland by direct extension. When prostate cancer is diagnosed a measure of histologic aggressiveness is assigned using the Gleason grading system in which the dominant and secondary glandular histologic patterns are scored from 1 well-differentiated to 5 undifferentiated and summed to give a total score of 2-10 for each tumor. The most poorly differentiated area of tumor . the area with the highest histologic grade often determines biologic behavior. The presence or absence of perineural invasion and extracapsular spread are also recorded. Prostate Cancer Staging The TNM staging system includes categories for cancers that are palpable on DRE those identified solely on the basis of an abnormal PSA T1c those that are palpable but clinically confined to the gland T2 and those that have extended outside the gland T3 and T4 Table 91-1 . DRE alone is inaccurate with respect to the extent of the disease within the gland the presence or absence of capsular invasion involvement of seminal vesicles and extension of disease to lymph nodes. Because of the inadequacy of DRE for staging the staging system was modified to include the results of imaging studies. Unfortunately no single test has proven to indicate accurately the stage or the presence of organ-confined disease seminal vesicle involvement or lymph node spread. Table 91-1 Comparison of Clinical Stage by the TNM Classification System and the Whitmore-Jewett Staging System TNM Stage Description Whitmore-
