A patient has a small, firm, asymptomatic bump in the lower vestibule. Histologic examination shows normal, mature bone and overlying normal soft tissue. What is the most likely diagnosis?

A benign bony exostosis or torus is composed entirely of normal, mature bone, which is why histologic examination (if performed at all, since these are usually diagnosed clinically without biopsy) would show unremarkable, normal bone and overlying soft tissue — distinguishing it from a true neoplasm, which would show abnormal/atypical tissue architecture.