It's helpful to know precisely what that “benign mass” was in terms of the patho-histological report. Every tumor that is surgically removed must be examined by a pathologist. Only the pathologist can determine the precise diagnosis and is the specialist capable of determining if the tumor is completely removed or not. Any benign tumor that is not removed completely can recur. Malignant transformations of some benign tumors are possible. Therefore, you may want to consult the pathologist who assisted during the removal of the mass or request your records and bring them to a pathologist who can translate the notes for you.