Spontaneous Testicular Teratomas in an Inbred Strain of Mice

Abstract

Testicular teratomas develop in about 1% of strain 129 males. These tumors grow progressively and are composed of many types of embryonic and adult tissues foreign to the testes. Teratomas were seen in very young strain 129 mice, and the incidence does not increase with advancing age. About 5% of 129 strain males exhibit another pathological condition, small testis, characterized by reduction in size of the testis through degenerative changes. Both teratoma testis and small testis occur about 3 times more frequently on the left side than the right, and it is suggested that similar etiological factors, which may be associated with gonadal migration, are involved. There seems to be correlation between size of a teratoma and number of tissue types it contains. The simplest teratomas examined were composed of undifferentiated embryonic tissue, nervous tissue, and cysts lined with cuboidal epithelium. More complex tumors contained several additional tissue types. It is suggested that differentiated elements stem from pluripotent embryonic-type cells. Fifteen spontaneous teratomas were transplanted. Of these, all took but only 1 developed into a rapidly growing transplantable tumor. This transplantable tumor consists of undifferentiated cells which grow both subcutaneously and in ascitic fluid. It is pointed out that an inbred strain of mice in which a relatively large percent-age of males develop testicular teratomas may be an important tool in the study of some hitherto unexplored aspects of the biology of these interesting growths.