Utility of immunostaining of HSD3B1 in evaluation for trophoblastic differentiation: A case report of urothelial carcinoma after chemotherapy

Abstract

Background: Trophoblastic differentiation, when observed, indicates a pathological condition that holds clinical significance as it predicts a poor prognosis. It is difficult to differentiate trophoblastic differentiation from other similar cytomorphological changes, and sensitivity and specificity of β-hCG, conventional trophoblastic differentiation marker, are limited. Case: A male patient in his late 70s presented with a bladder tumor measuring 11 cm in diameter as detected by CT scan. Urine cytology indicated high-grade urothelial carcinoma, so he underwent chemotherapy. After tumor reduction, radical cystectomy was performed. Histological examination of resected tumor revealed, in addition to conventional high-grade urothelial carcinoma, pale cells with distinct cell borders and mononucleated or multinucleated giant cells suggesting trophoblastic differentiation in the tumor. Immunohistochemical staining showed approximately 1% positivity for β-hCG in giant cells, while HSD3B1, a marker with excellent sensitivity and specificity for intermediate trophoblasts and syncytiotrophoblasts, was positive in most giant cells. Urine cytology before chemotherapy showed few giant cells, while post-chemotherapy urine cytology revealed numerous mononucleated and multinucleated giant cells. Immunocytochemical staining showed approximately 1% positivity for β-hCG, but approximately one-quarter of the giant cells were positive for HSD3B1. Final diagnosis of urothelial carcinoma with trophoblastic differentiation was made. Conclusion: The experience of the present case recommends immunostaining of HSD3B1 when giant cells are observed in pathological specimens of the patients undergoing chemotherapy for urothelial carcinoma to rule out cellular damage due to chemotherapy.