Embryoma (sialoblastoma) of salivary glands.

There are four clinicopathologic categories of the exclusively major salivary gland tumors that present in the perinatal period. The two with the smallest representation among the 20 cases reported to date are those with a hamartomalike appearance and those with benign adult equivalents--the pleomorphic and monomorphic adenomas. Five cases have been undifferentiated or basaloid salivary carcinomas. Embryomas (sialoblastomas) are the most numerous. These tumors manifest a histologic phenotype like that of the epithelial anlage of the salivary glands, albeit in an arrested state of differentiation.