Adenocarcinoma not otherwise specified (NOS) is a rare lesion of the salivary glands that can resemble a mucocele. This article presents a case involving a long-standing lesion that was presumed to be a mucocele but was, in fact, a low-grade carcinoma. The subsequent excision is described and follow-up recommendations are made. A review of the literature and characteristics of the lesion also are included.