A mum says she is watching her four-year-old son fight for his life after his tummy ache turned out to be a rare kidney disease. Leslie Cooke was diagnosed with Wilms tumour after he woke up to find a tennis-ball-sized lump on his stomach. His cancer is categorised as Stage 4, the most advanced phase, with the disease spreading to his lungs, liver, main artery and backbone. His mum Jessica said: “He’s amazing. He’s strong, he’s a fighter and he’s a hero. “I mean it when I say I’ve watched him fight for his life.” The 32-year-old from Milton Regis, near Sittingbourne, also has two daughters, Al…