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 (i.e., 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- Jewett Stage Description T1a Nonpalpable, with 5% or less of resected tissue with cancer A1 Well differentiated tumor on few chips from one lobe T1b Nonpalpable, with >5% of resected tissue with cancer A2 Involvement more diffuse T1c Nonpalpable, detected due to elevated serum PSA T2a Palpable, half of one lobe or less BIN Palpable, < one lobe, surrounded by normal tissue T2b Palpable, > half of one lobe but not both lobes B1 Palpable, < one lobe T2c Palpable, involves both lobes B2 Palpable, one entire lob e or both lobes T3a Palpable, unilateral extracapsular extension C1 Palpable, outside capsule, not into seminal vesicles T3b Palpable, bilateral extracapsular extension T3c Tumor invades seminal vesicle(s) C2 Palpable, seminal vesicle involved M1 Distant metastases D Metastatic disease Source: Adapted from FF Schroder et al: TNM classification of prostate cancer. Prostate (Suppl) 4:129, 1992; and American Joint Committee on Cancer, 1992. . Chapter 091. Benign and Malignant Diseases of the Prostate (Part 4) Pathology The noninvasive proliferation of epithelial cells within ducts is termed prostatic intraepithelial. 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. 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