IMMUNOHISTOCHEMICAL DIFFERENTIATION OF METASTASES OF RENAL CARCINOMASVERSUS OTHER CARCINOMAS WITH ANTI-GAMMA-CT MONOCLONAL-ANTIBODY 138H11

Aims: Adenocarcinomas account for about 60% of metastatic cancers of u nknown primary (CUP) site. In such a clinical CUP situation, histopath ologists are challenged to differentiate renal cell carcinomas (RCC) f rom other adenocarcinomas with similar immunophenotypes, especially ch emotherapeutically treatable mammary and ovarian carcinomas. Methods a nd results: Recently, we produced a monoclonal antibody (mAb), designa ted 138H11, against human gamma-glutamyl-transferase (gamma GT), which stained over 98% primary clear cell and chromophilic RCC on frozen se ctions. The 138H11 epitope could not be stained using conventional tec hniques in most paraffin-embedded sections of the same origin, due to destruction by formalin fixation below the detection level. Here, we d emonstrate that mAb 138H11 can specifically stain gamma GT in parrafin -embedded primary and metastatic RCC after enhancement with an ultrase nsitive immunohistochemical method, Mie analysed a selected subgroup o f adenocarcinomas with immunophenotypes which would not allow a differ entiation from RCC in a CUP situation, We found a predominantly membra nous expression of the 138H11 target antigen in 26/51 primary RCC and 15/34 metastatic RCC. In contrast, all 43/43 primary ovarian and bronc hial carcinomas as well as 54/54 metastases of ovarian, mammary, bronc hial and gastric carcinomas were negative for mAb 138H11, Conclusions: The data suggest that mAb 138H11 is useful for the immunohistochemica l differentiation of RCC from other metastatic adenocarcinomas if the primary site of the tumour is not known.