What Are The Symptoms Of Malignant Tumor?

My 2 year old nephew recently developed a squint to the left eye which i believe happened very suddenly, he was admitted to hospital over night for observation, he has recently had a MRI scan and the parents have been told he has 2 shadows on his spine and in his space of skull their is tissue growing which should not be growing, sorry to be vague, but can you shed any light on this.The child has no signs of any nuerological disorders, no limb weakness, no sensory or motor loss. Is this something of concern i.e. a start of a malignant tumour or could it be benign in natuure