PTGS2 and neoplasm: It should therefore be considered mandatory for all cancer patients, especially in such cases where the tumour cells express COX-2 or COX-1, to restrict the dietary intake of AA, at the same time as the total intake of other unsaturated fatty acids (especially omega-3 fatty acids and oleic acid) that compete with AA for incorporation in the same positions in the membrane lipids of the tumour cells should be increased.