OCM and neoplasm: The H&E staining of the grafted tumor sections clearly showed that the OCM1-derived tumors consisted of both spindle and epithelioid cells (Fig. 1C1,E1) while C918-derived tumors were composed of only epithelioid cells (Fig. 1D1,F1) though these two UM cell lines were morphologically stable in monolayer culture (Fig. 1A,B and inserts), suggesting that spindle cells could become epithelioid in grafted tumors but not vice versa.