Bilateral ovarian teratomas in a mouse.

Solid ovarian tumors of all types are very uncom mon in the lower animals, and teratomas of the ovary are exceedingly rare. In @,000autopsies on mice, Slye, Holmes, and Wells (1@) found only 46 with solid tumors of the ovary, and of these only one was a teratoma. Many of the mice they cx amined, moreover, were from stock having a high incidence of tumor formation. The present paper reports the spontaneous occurrence of bilateral teratomas of the ovary in a mouse of the “Swiss― albino strain. The mass in the right ovary measured @3X 19 X @0 mm. and that in the left ovary 17 X 10 X 10 mm. (Fig. 1). Both presented a mottled appearance suggesting, in the gross, the heterogeneous composition which was verified in histological sections. In the smaller tumor some remaining ovarian tissue was found, including one small follicle. The right ovary ap peared to be almost entirely replaced by the teratomatous growth. The two tumors were similar in composition, consisting of several recognizable embryonic tissues in varying degrees of differentiation. There were large areas of nervous tissue (Fig. 3). Other areas contained glandlike structures, cysts filled with mucoid secretion, gastric mucosa, squamous cells forming epitheial pearls, and small nodules of cartilage (Fig. 5). Extending over a considerable portion of the surface of one of the tumors was a deeply basophilic layer of cuboidal cells resembling the germinal epithelium which normally covers the ovary. In one locality, illustrated in Figure 4, the cells of this epithelium gradually became columnar and assumed the appearance of mucous cells. Extend ing inward from the mucus-secreting epithelium were tubular structures resembling typical gastric glands in which both chief and parietal cells were recognizable. The germinal epithelium of the