Does pT2b prostate carcinoma exist? Critical appraisal of the 2002 TNM classification of prostate carcinoma

BACKGROUND Clinicopathologic staging of prostate adenocarcinoma provides a method for assessing the extent of tumor and predicting patient prognosis. The American Joint Committee on Cancer (AJCC) TNM staging system has undergone recent revisions for T2 prostate tumors. T2 tumors currently are subclassified as T2a (less than one‐half of one lobe involvement), T2b (greater than one‐half of one lobe involvement), and T2c (bilateral involvement). Despite general acceptance of the system, controversy and uncertainty still exist with regard to the application of the TNM staging system, particularly the use of the T2 staging subclassification. METHODS The study population was comprised of 369 patients with prostate carcinoma who were treated with radical retropubic prostatectomy. Radical prostatectomy specimens were evaluated histologically by complete embedding and whole‐mount processing. Tumor specimens were staged initially using the 1998 AJCC TNM system and then reevaluated according to the 2002 TNM staging guidelines. RESULTS The weights of the prostate specimens ranged from 14–149 g (median, 38 g). Prostate tumor specimens were multifocal in 312 patients (85%). The majority of the specimens were classified pathologically as T2 (n = 276 [75%]). Using the 2002 TNM staging criteria, 54 of the tumor specimens (15%) were classified as pT2a, 222 (60%) were pT2c, 75 (20%) were pT3a, and 18 (5%) were pT3b. No pathologic T2b tumor specimens were identified. CONCLUSIONS Taking into consideration the average weight of the prostate specimens (38 g), as well as the predominance of tumor multifocality, it would be unusual to identify tumors involving greater than one‐half of 1 lobe (approximately an 8‐cm3 tumor) without involving the other lobe. The authors question the existence of a true pT2b tumor. Cancer 2004. © 2004 American Cancer Society. Taking into consideration the average weight of prostate specimens (38 g), as well as the predominance of tumor multifocality, it would be unusual to identify tumors involving greater than one‐half of 1 lobe (approximately an 8‐cm3 tumor), without involving the other lobe. The current study did not support a distinct subclassification for tumors occupying greater than one‐half of a single lobe, but fewer than 2 lobes (pT2b). The authors questioned the existence of a true pT2b tumor.