Fig. 2. Immature teratoma. A. An immature teratoma is encapsulated and grossly similar to its benign counterpart, the mature teratoma. The main difference is the immature teratoma is solid rather than cystic. B. An immature teratoma reveals a variegated appearance with areas of necrosis and cystic changes. C. An immature teratoma reveals mixtures of mature and immature tissues reminiscent of the developing stages of embryonic tissues. The most common pattern is seen here (e.g., an immature neural epithelium [neuroepithelial rosettes]).