Transitional cell carcinomas of the ovary and bladder are immunophenotypically different

Aims Transitional cell carcinoma (TCC) of the ovary is a subtype of ovarian cancer whose main characteristic is its histological resemblance to TCC of the bladder. Thrombomodulin (TM), a surface glycoprotein commonly expressed in normal and neoplastic urothelium, has been proven to be a good marker for TCC of the bladder. To better define the phenotype of TCC of the ovary, we investigated TM, cytokeratin 20 and carcinoembryonic antigen (CEA) expression in 15 TCCs of the ovary and compared their phenotype with that of 20 TCCs of the bladder, and 20 serous and 10 endometrioid carcinomas of the ovary. Methods and results Immunostaining was performed on formalin‐fixed, paraffin‐embedded tissue sections using the avidin–biotin–peroxidase complex method. All 20 TCCs of the bladder stained for TM and cytokeratin 20, and 13 stained for CEA. None of the TCCs of the ovary reacted for TM or cytokeratin 20, and only two expressed CEA. All of the serous and endometrioid carcinomas were negative for TM and cytokeratin 20. CEA positivity was observed in two of the serous carcinomas, but in none of the endometrioid carcinomas. Conclusion The immunophenotype of TCC of the ovary is similar to that of other surface carcinomas of the ovary, but differs from that of TCC of the bladder. Since immunohistochemical procedures are often used in the diagnosis and classification of both primary and metastatic tumours, it is important to be aware of these differences in immunophenotype.