Teratoma of the pineal body is surprisingly rare considering the many possibilities for that type of tumor formation inherent in the body. The literature contains reports of only thirteen cases of proved teratoma, four cases of teratoid tumor and one case of chorionepithelioma of the pineal body. These constitute approximately 10 per cent of all the reported tumors of the pineal body. To this series there is here added a new case, which is unique in that it presents for the first time all stages in the development of adult teeth.
DEFINITION AND CLASSIFICATION OF EMBRYONAL NEOPLASMS1
Considerable confusion exists in the literature on the subject of embryonal and mixed tumors of the pineal body, largely because of the lack of uniformity in the terminology applied. At the very beginning of this paper, therefore, definition and classification of the terms which we shall use will be made. This classification