There is no written rule on how big a tumor can get. Generally, skin tumors are somewhere between 0.3 to 2 inches big. However, some tumors can reach up to 4 inches. The tumor size depends on the type of tumor. Minor, benign tumors are generally not invasive, and they are small. This is because they don’t progress to other parts of the body. For instance, papilloma, or warts, can reach up to 1.5 inches, which is quite big. Even though this is a benign tumor that doesn’t have severe repercussions in most cases, the tumor can get pretty big. On the other hand, some invasive, malignant tumors can be pretty big, too as they spread rapidly. However, the important thing to know is that the size of a tumor doesn’t positively correlate with the invasiveness of a tumor.