Can immunohistochemistry enhance the detection of micrometastases in pelvic lymph nodes from patients with high-grade urothelial carcinoma of the bladder?

Immunohistochemistry for keratin has enhanced our ability to detect micrometastases in certain cancer patients with negative lymph nodes by routine histologic examination of H&E-stained sections. However, there is no information about micrometastasis of bladder cancer. We performed immunohistochemistry for keratins on 159 pelvic lymph nodes, which were negative for metastatic tumors on routine H&E-stained sections, from 19 patients with high-grade muscle invasive urothelial bladder cancer. In 1 man, 1 lymph node contained a keratin-positive micrometastasis that was not present on the original H&E-stained slide. However, the metastasis was seen readily on a new H&E-stained section prepared from the paraffin block adjacent to the keratin-stained section. Immunohistochemical analysis for keratins revealed no additional case of micrometastasis of urothelial carcinoma of the bladder. The perinodal fibroadipose tissue of a lymph node from a woman contained a few keratin-positive benign glands of endosalpingiosis. A thorough examination of the H&E-stained sections is the best method for detecting lymph node metastases of urothelial carcinoma from the bladder. There is a potential risk for misdiagnosis of metastases by using immunohistochemistry or polymerase chain reactions for keratins because of the occasional presence of benign epithelial cells in pelvic lymph nodes and associated connective tissue.