Immunohistochemical study of proliferating cell nuclear antigen (PCNA) in endometrial carcinoma with argyrophil cells

We performed an immunohistochemical study of argyrophil cells in 10 endometrial carcinomas using the monoclonal antibody PC 10 to detect proliferating cell nuclear antigen (PCNA). Formalin-fixed, paraffin-embedded sections of 10 endometrial carcinomas containing argyrophil cells which are chromogranin positive (four containing type I cells, two type II, and four mixed-type I and type II) were stained with monoclonal antibody PC 10. In addition, one of the tumors with mixed-type cells was transplanted into nude mice, and the tumors which developed in subpassages were also analyzed for PCNA. Argyrophil cells in 10 endometrial carcinomas were found to be negative immunohistochemically for PCNA, regardless of their type, suggesting that they are not proliferating. Surprisingly, however, all subpassaged tumors contained argyrophil cells which were also negative for PCNA. From these results, it may be postulated that argyrophil cells were induced through differentiation to neuroendocrine direction of neoplastic cells.