Ascites tumors in CBA mice. 2. Ultrastructural aspects on ascites conversion.

We have studied four syngeneic murine tumors, a fibrosarcoma, a squamous cell carcinoma and their two ascites-converted counterparts, by transmission electron microscopy. The ascites tumors were investigated both as cell suspensions (AA-tumor) and as solid tumor (AS-tumor). We have also studied the ascites tumors, enzymatically produced cell suspensions of the AS-tumors and solid original tumors by scanning electron microscopy. The two ascites tumors are totally de-differentiated and lack intercellular junctions. This, we think, is a prerequisite for ascites growth. But the ascites tumors show no peculiar ultrastructural features in comparison with other undifferentiated malignant tumors. We found no morphological cell alternations by the enzymatical dissociation procedure used to bring the solid tumors into suspension. Differences between the AS and AA tumors can be ascribed to differences in proliferation rates.