Hi... Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns... As per your complain the bumps over the back of tongue that are painless, small in size does not seems to be due to any pathology as they are Circumvallete Papillae which contains taste buds and are arranged in typical V shaped pattern and are naturally slightly raised structures.. There is no need to think of cancer as it is not at all due to it.. You need not to worry as nothing seems pathological and to further confirm consult an Oral Physician and get evaluated.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.