Unusual Occurrence of Endometrial Sarcomas in Hybrid Mice2

Abstract

Eight endometrial sarcomas and 1 leiomyosarcoma in (C57BL/6 × DBA/2)F₁ mice were described. The frequency of the endometrial sarcomas reached 37% in animals over 18 months old. Electron microscopic studies showed that these tumors probably arose from an undifferentiated mesenchymal stromal cell normally present in senescent mouse endometrium. These tumors could be readily transplanted and grew better in females than males. They did not respond to endogenous or exogenous progesterone.