From the research point of view--ovarian teratomas, especially mature ones, are an interesting group of germ-cell tumors of the ovary. The WHO classification, which is not simple but includes all tumors that arise from germ cells, emphasizes the complexity of this group. Their complex pathophysiology is also very interesting from the clinical point of view because of their frequent occurrence,especially among young women of reproductive age. Mature ovarian teratomas are benign germ-cell tumors, but in rare cases, especially when they contain solid elements, peritoneal implants may be present which can stimulate malignant processes. Dermoid cysts, a subtype of ovarian teratomas, arise from totipotential germ cells and may therefore contain elements of all three germ layers, although ectodermal structures usually predominate. Radical surgical treatment is not necessity for this type of tumor because conservative surgery usually brings full recovery.However, they make perfect material for gaining interesting information regarding oocyte maturation and such critical cellular functions as proliferation, migration, differentiation, and apoptosis.There are still no unequivocal conclusions related to the role of mutation in genes which influence the mechanisms involved in control of the cell cycle and which may play important roles in the development of ovarian teratomas. In this review the roles of the Patched/Hedgehog and PI3K/Akt pathways and cyclin D protein in the neoplastic transformations of the germ cells are described.