[Cytomorphological reappraisal of choriocarcinoma cells--a proposal of a four cell pattern]

It is generally accepted that choriocarcinoma is composed of two cell types: syncytiotrophoblast (ST)-like cells and cytotrophoblast (CT)-like cells. In normal and molar pregnancy, there is another population of trophoblast in the cell column, the decidua and so forth. They are designated intermediate trophoblast (IT) and multinuclear IT. It remains to be clarified whether IT-like cells and multinuclear IT-like cells are observed in choriocarcinoma. In the present study, choriocarcinoma cells were reappraised cytomorphologically in three cases of uterine choriocarcinoma and additional three cases of metastatic choriocarcinoma. The results were as follows: 1. Choriocarcinoma cells could be classified into four cell types: ST-like cells, CT-like cells, IT-like cells and multinuclear IT-like cells. 2. IT-like cells predominated in metastatic lesions as compared with primary lesions. It seemed that choriocarcinoma shows both differentiations which take place in villous and extravillous trophoblasts of normal and molar pregnancy. IT-like cells were found to infiltrate into vessel walls, which, together with the predominance of IT-like cells in metastatic lesions, suggests that IT-like cells contribute greatly to the hematogenous metastasis in choriocarcinoma. The presence of ST-like cells, CT-like cells and multinuclear IT-like cells in metastatic lesions may indicate a germinative nature of IT-like cells.