CNS myelin and synapses in a spontaneous mouse ovarian teratoma showing neural differentiation. An immunohistochemical and electron microscopic study.

A morphologic (light-, electron microscopic, and immunohistochemical) study of a spontaneous ovarian teratoma, originating in the LT strain of mice and showing predominantly neural differentiation, has revealed an unusually large number of mature myelinated axons and synapses within areas of well-differentiated neuroepithelium. Most of the myelin was determined to be of CNS origin by its staining characteristics with the LFB-PAS stain, the absence of reticulin fibers by light microscopy and of basal laminae by electron microscopy in relation to the myelin sheaths, the presence of associated cells identified morphologically as oligodendrocytes, and by the strongly positive immunohistologic reaction obtained for myelin basic protein. Most synapses likewise appeared to be of the CNS type. This murine ovarian teratoma may therefore be a useful tool for the study of neoplastic myelinogenesis and synaptogenesis.