Malignant transformation of mucinous ovarian cystadenomas of intestinal epithelial type.

We studied 116 benign and 18 borderline malignant mucinous ovarian cystadenomas. Their epithelial lining was compared with normal epithelium of the uterine cervix and that of the small and large intestines, by both light and electron microscopy as well as histochemically. This morphological and histochemical analysis enabled us to subdivide mucinous cystadenomas into cervical, mixed and intestinal epithelial types. The epithelial cells of intestinal type tumours exhibited histochemical reactions very similar to, or identical with, those found in both immature and mature cells of intestinal mucosa. Malignant transformation was found in intestinal type mucinous cystadenomas only. Ultrastructural investigations of six neoplasms (four of intestinal and two of cervical epithelium type) confirmed the results found with the light microscope.