Placental proteins in high‐grade urothelial neoplasms. An immunohistochemical study of human chorionic gonadotropin, human placental lactogen, and pregnancy‐specific beta‐1‐glycoprotein

We examined the presence of human chorionic gonadotropin (HCG) in 16 low‐grade and 47 high‐grade urothelial neoplasms, including two cases with trophoblastic‐like differentiation. In HCG‐positive tumors, the presence of human placental lactogen (HPL) and pregnancy‐specific beta‐1‐glycoprotein (SP‐1) also was assessed. HCG immunoreactive cells were found in nine of the 47 high‐grade tumors (19%), whereas none of the low‐grade tumors were positive for HCG. This hormone was predominantly detected in the most undifferentiated and pleomorphic areas; however, HCG‐positive cells also were found in areas of carcinoma in situ and well‐differentiated transitional cell carcinoma in two cases. The serum HCG level was increased in two of the four cases studied. HPL and SP‐1 immunoreactive cells were observed in seven and five cases, respectively, and it was found that tumors positive for SP‐1 also were positive for HPL. Five tumors, including the two with trophoblastic differentiation, contained the three placental proteins. The HPL and SP‐1 immunostained cells were usually found in the same areas of the tumor that were positive for HCG, but there was always a lower number of HPL and SP‐1 immunoreactive cells than HCG immunoreactive cells. In one case, HPL and SP‐1 could be found in areas of well‐differentiated transitional cell carcinoma. These findings suggest that the morphologic and functional trophoblastic differentiation in urothelial carcinomas is a progressive phenomenon evolving from transitional cell carcinomas.