An unidentified lipid prevalent in tumors

An unidentified lipid was found in five different tumor sources. It was not found in liver, bone marrow or plasma from tumor‐bearing animals, nor in the extracellular fluid supporting growth of Ehrlich ascites cells. The polarity of the unidentified component was similar to that of a glyceryl ether diester, and it was isolated in milligram amounts by preparative thinlayer chromatography. Neither methyl esters of fatty acids, vinyl ether diesters nor quinones were found in the structural makeup of this lipid. Thin‐layer chromatography of the purified unidentified tumor lipid on Ag‐impregnated silica layers revealed two main components of intermediary unsaturation. Saponification of the unidentified tumor lipid, when water washing was omitted, yielded two components that migrated at R f 's identical to those of free fatty acids and dihydroxy glyceryl monoethers. Neither acetate‐1‐ 14 C nor palmitic‐1‐ 14 C acid (single injections) was found to be incorporated into the unidentified lipid of a mature rat tumor.