Does the gross prosector impact pT3 subclassification or lymph node counts in bladder cancer?: Beyond the Abstract

Urinary bladder cancer is the fourth most common cancer to occur in men. A cancer staging system is used to estimate the potential aggressiveness of urinary bladder tumors. The depth of invasion has been shown to significantly affect the expected survival of patients. Higher stage tumors require more aggressive therapy and have worse expected patient survival outcomes. 

One parameter that affects the staging of urinary bladder cancer is whether the tumor invades the fat tissue directly outside the bladder. There are three options: (1) the tumor does not invade the fat tissue and receives the lower stage (≤pT2b); (2) the tumor visually does not invade the fat but is found to invade the fat tissue when examined under a microscope and receives an intermediate stage (pT3a); (3) the tumor is found to invade the fat tissue on visual examination and microscopic examination and receives the higher stage (pT3b) (Figure 1A). The person who visualizes the bladder and determines, without a microscope, if the tumor has invaded the fat is the gross prosector. Some studies show no difference in survival between tumors that invade the fat microscopically versus on visual examination, despite the fact that a tumor that invades on visual examination is theoretically more aggressive. 

Another factor that affects the staging of urinary bladder cancer is whether the tumor invades local or distant lymph nodes. Lymph node invasion by the tumor is also correlated with higher stage tumors and worse patient outcomes. Lymph nodes near the bladder are removed at the time of surgery, but it is unclear how many lymph nodes should be removed. Some studies show a benefit to removing a higher number of lymph nodes (a more extensive surgery with more risk for complications), while other studies show no benefit. The gross prosector also has an impact on the number of lymph nodes retrieved at the time of surgery because he or she identifies the lymph nodes and reports this number Figure 1B-1C).

Because of the grosser impact on tumor staging and lymph node count, proper documentation of the presence or absence of tumor fat invasion as well as accurate lymph node identification are important. In this study, we evaluated the role of the gross prosector in tumor staging and lymph node count. Doing so would allow us to determine if the gross prosector impacts these variables, as this may be a potential source of the reported differences in significance described in previous studies.

We found that there was a high frequency of cases (17%) in which the gross prosector did not document the visual examination of whether or not the tumor invaded the bladder fat tissue. Cases in which the gross prosector did not document the tumor invasion status were more likely to be classified as having a tumor with a lower stage (pT3a, 75%). Educational interventions given to the gross prosectors decreased the frequency of cases in which the gross prosector did not document the tumor fat invasion status (33% to 5%), and also increased the ratio (pT3b:pT3a) of cases given a higher tumor stage compared to a lower stage. We also found that it was common for gross prosectors to overcount lymph nodes (22%). Gross prosectors that did a lower number of cases had more lymph packets with no nodes counted.

In conclusion, the gross prosector is a variable to consider in the methodology and comparison of bladder cancer research studies, and evaluation of the gross prosector may be helpful to improve the quality of bladder cancer pathologic reporting.

Figure 1
A) Bladder cancer involving the fat surrounding the bladder. The visual assessment by the gross prosector will determining the stage given (pT3a vs pT3b). In this case the gross prosector documented fat invasion, which was confirmed with microscopy and the tumor was given the higher stage (pT3b).
B) Lymph node packet from a bladder surgery with an unknown number of lymph nodes.
C) The gross prosector has evaluated the lymph node packet and has identified 4 lymph nodes (2 small, 2 large).

Written by: Eric M. Tretter, B.S. and Debra L. Zynger, M.D., The Ohio State University Medical Center, Department of Pathology (E.M.T., D.L.Z.)

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