Because<unk>  usually does not cause symptoms, it is hard to determine prevalence.<unk>  is rarely reported in the literature. The prevalence of<unk>  reportedly ranges from 1 to 90%. This variation in prevalence is largely dependent upon the method of investigation used and how extensive the workup is. With most<unk>  tissue being asymptomatic, it is likely the prevalence is higher than typically reported.
Ectopic thymus
Abscess of thymus
Cervical thymic cyst
Tracheal agenesis
Persistent thyroglossal duct
Salivary gland atresia
Ectopic salivary gland tissue
Salivary gland aplasia