The embryonal carcinoma of the parotid gland. A rare example of an embryonal tumor.

Embryonal tumors are a neoplastic proliferation of cells of organ rudiments. Morphologically, these tumors are similar to the developmental stages of these organ rudiments. Embryonal tumors of the salivary glands have not been previously described. In the salivary gland register, reviewing the years 1965-1982 (n = 8043), we diagnosed 2,878 tumors of the salivary glands, of these 73 were tumors in children. One case was a malignant epithelial tumor in a 12-year-old boy, which showed the criteria of an embryonal carcinoma in light- and electron microscopy. The tumor revealed solid undifferentiated areas, epidermoid structures with keratinization and acinic structures. Immunhistochemically, the better differentiated epidermoid cells reacted positively with anti-CEA and anti-keratin, the acinic cells were positive with anti-amylase. The ultrastructure was characterized by primitive ductular epithelial cells and acinic cells with their typical morphological features. The embryonal carcinoma has to be distinguished from undifferentiated carcinomas of the salivary glands, which consist of primitive ductular structures only. The failure to detect other tumor markers (lactoferrin, tissue polypeptid antigen) indicates that poorly and well differentiated areas can exist simultaneously in embryonal carcinomas.