Diagnostic problems within the oral cavity may be associated with lesions of the odontogenic apparatus, salivary glands, bone, mucosa, and connective tissue. Some lesions are unique to the oral cavity, others have a systemic distribution. Several unique and controversial lesions have been selected for discussion, including (1) necrotizing sialometaplasia, a benign salivary gland disease easily mistaken for malignancy; (2) verrucous lesions including verrucous carcinoma, verrucous hyperplasia, and papillary carcinoma; (3) spindle-cell carcinoma, which is often confused with sarcoma; (4) named and unnamed embryonic rests, which may resemble metastatic carcinomas; (5) dental pulp mistaken for odontogenic myxoma; and (6) granular cell tumor with associated pseudoepitheliomatous hyperplasia.