Many teeth have been mistakenly extracted or endodontically treated because of an incorrect diagnosis of orofacial pain including toothache, A case report of persistent toothache originating from a malignant lymphoma of left maxilary sinus is presented. Root canal therapy and extraction of left upper quadrant teeth from canine to second molar did not resolve the chief complaint. The patient was referred to a neurologist and was diagnosed with a malignant lymphoma, a rare lesion of the maxillary sinus. The case stresses the importance of malignant neoplasms of maxillary sinus as a potential etiologic factor in the differential diagnosis of orofacial pain.