Spontaneously dispersible concentrates and aqueous microemulsions with steryl retinates having anti-tumor activity

A spontaneously dispersible concentrate which forms an ultramicroemulsion when diluted with water or a glucose solution comprising:

• 0.001 to 15% by weight of one or a combination of steryl ester compounds selected from the group consisting of compounds of formulae (I) to (XII):
• ##STR31## wherein R.sub.1 represents a C.sub.1-10 alkyl or a C.sub.2-10 alkenyl group and R.sub.2 represents a member selected from the group consisting of formulae (XVI) and (XVII):
• ##STR32## wherein n is 1, 2, 3, 4, or 5, and R.sub.5 represents a radical selected from the group consisting of ##STR33## 0to 40% by weight of a pharmaceutically acceptable solvent or solvent mixture which acts as a hydrotropic agent or co-emulsifier;
• 0. 001 to 90% by weight of a pharmaceutically acceptable surfactant or surfactant mixture;
• 0 to 10% by weight of a vitamin or provitamin,
• up to 10% by weight of a free fatty acid, and
• a pharmaceutically acceptable carrier or diluent.