Bladder Cancer. Pathology & Selection of Treatment.
Pathology & Selection of Treatment
Ninety-eight percent of primary bladder cancers are epithelial malignancies, with the majority being transitional cell carcinomas (90%). These latter cancers most often appear as papillary growths, but higher-grade lesions are often sessile and ulcerated. Grading is based on histologic architecture: size, pleomorphism, mitotic rate, and hyperchromatism. The frequency of recurrence and progression is strongly correlated with grade. Whereas progression may be noted in few grade I cancers (19–37%), it is common with poorly differentiated lesions (33–67%). Carcinoma in situ is recognizable as a flat, nonpapillary, anaplastic epithelium and may occur focally or diffusely, but it is most often found in association with papillary bladder cancers. Its presence identifies a patient at increased risk of recurrence and progression.
Adenocarcinomas and squamous cell cancers account for approximately 2% and 7% (respectively) of all bladder cancers detected in the USA. The latter is often associated with schistosomiasis, vesical calculi, or chronic catheter use.
Bladder cancer staging is based on the extent of bladder wall penetration and the presence of either regional or distant metastases. The TNM classification of the American Joint Cancer Committee for bladder cancer is shown in Table 23–11.
Table 23–11. TNM staging system for bladder cancer.
T: Primary tumor
Tx Cannot be assessed
T0 No evidence of primary tumor
Tis Carcinoma in situ (CIS)
Ta Noninvasive papillary carcinoma
T1 Invasion into lamina propria
T2 Invasion into superficial layer of muscularis propria
T3a Invasion into deep layer of muscularis propria
T3b Invasion through serosa into perivesical fat
T4a Invasion into adjacent organs
T4b Invasion into pelvic sidewall
N: Regional lymph nodes
Nx Cannot be assessed
N0 No regional lymph node metastasis
N1 Metastasis in a single lymph node £ 2 cm
N2 Metastasis in a single lymph node > 2 cm and < 5 cm or multiple
nodes none > 5 cm
N3 Metastasis in lymph node > 5 cm
M: Distant metastasis
Mx Cannot be assessed
M0 No distant metastasis
M1 Distant metastasis present
The natural history of bladder cancer is based on two separate but related processes: tumor recurrence and progression to higher stage disease. Both are related to tumor grade and stage. At initial presentation, approximately 50–80% of bladder cancers will be superficial: Ta, Tis, T1. Lymph node metastases and progression are uncommon in such patients when they are properly treated, and survival is excellent at 81%. Patients with superficial cancers (Ta, T1) are treated with complete transurethral resection and the selective use of intravesical chemotherapy. The latter is used to prevent or delay recurrence. Patients who present with large, high-grade, recurrent Ta lesions, T1 cancers, and those with carcinoma in situ are good candidates for intravesical chemotherapy. Patients with more invasive (T2, T3) but still localized cancers are at risk of both nodal metastases and progression, and they require more aggressive surgery, irradiation, or the combination of chemotherapy and selective surgery or irradiation due to the much higher risk of progression compared to patients with lower-stage lesions. Patients with evidence of lymph node or distant metastases should undergo systemic chemotherapy initially.