Cytokeratin 7 and cytokeratin 20 in primary urinary bladder carcinoma and matched lymph node metastasis

Background.-Cytokeratin 7 (CK7) and cytokeratin 20 (CK20) are 2 types of in termediate filament protein. Expression of CK7 is seen in the majority of p rimary urinary bladder carcinomas. CK20 is restricted to superficial and oc casional intermediate cells of the normal urothelium of the bladder. Aberra nt CK20 expression has been documented in urothelial carcinoma and has prov ed useful as an ancillary diagnostic aid for urinary bladder tumor. Our hyp othesis is that the pattern of CK7 and CK20 expression in metastatic urothe lial carcinoma duplicates the expression of the same markers in the primary tumors. Therefore, immunohistochemical staining of metastatic tumors for t hese 2 markers may be helpful for differential diagnosis in ambiguous metas tatic tumor deposits. Objective.-To determine the concordance of CK7 and CK20 expression in prima ry bladder urothelial carcinoma and the matched lymph node metastasis. Design.-We studied 26 patients with lymph node metastases who underwent rad ical cystectomy and bilateral lymphadenectomy for bladder carcinoma. Immuno histochemical staining for CK7 and CK20 was performed on formalin-fixed par affin-embedded tissues containing primary cancers and lymph node metastases . Results.-ln all cases, there was a concordant expression of CK20 in the pri mary cancer and its matched lymph node metastasis. Twelve cases (46%) showe d positive CK20 immunoreactivity in the primary tumor and its matched lymph node metastases, whereas 14 cases (54%) were negative for CK20 in both the primary tumor and lymph node metastasis. All cases showed positive CK7 imm unoreactivity in the primary cancers and matched lymph node metastases. Conclusions.-CK20 immunoreactivity is reliably observed in metastases from bladder cancer when the primary tumor expresses CK20.