CPT® 61521-neurosurgery

Our surgeon excised two tumors. One in the right cerebellar region and the other in the midline vermian region. Our coder added Mod 22. Now Medicare wants a statement requesting what extra work has been done. My question is that how many tumors are covered under this CPT® code. Is modifier 22 warranted? I looked through the AANS Coding guide and none of their samples have any modifiers on them.