Immunohistochemical and ultrastructural study on erythropoiesis in hepatoblastoma

Eighteen cases of hepatocellular carcinoma in children were examined, and it was found that erythropoiesis exclusively appeared in the well differentiated type of hepatoblastoma. In such foci large immature erythroblasts were found among the tumor cells, whereas mature forms tended to gather in the subendothelial spaces or within sinusoids. Desmosome-like attachments were frequently found between immature erythroblasts and tumor cells. The tumor cells were well differentiated and had a distinct polarity. The erythropoietic foci were never found in lymph nodes, spleens and in the non-neoplastic hepatic tissues obtained by surgery or autopsy. Erythroblastic cells did not show an increase in number in the bone marrows. These findings indicate that hepatoblastoma cells in certain stages of differentiation have the capacity to induce the differentiation of pluripotent hemopoietic stem cells into the cells of erythrocytic series, or that the microenvironment composed of one or more tumor cells offer good soil for the differentiation of erythroblastic cells. There seems to be no intimate relationship between the production of alpha-fetoprotein by tumor cells and the appearance of erythropoiesis.