Pathology of mucinous ovarian cystadenomas. 2. Ultrastructural findings.

Fourteen mucinous ovarian cystadenomas of different grades of malignancy (7 benign, 4 borderline and 3 malignant) were investigated by electron microscopy. The main tumour cell type was a columnar mucous epithelial cell with short microvilli. With increasing grade of malignancy the shape and size of these cells became more irregular and the number of mucous granules in them decreased. Most of the mucous granules had a dense core and a less dense reticular component, which stained well with the periodic acid-silver methenamine (PASM) technique. Goblet cells with the usual ultrastructure were found rather frequently. The tumours in a given group of malignancy were relative similar to each other in their light and electron microscopic appearance. However, a number of tumours contained argyrophil and argentaffin cells in addition to the columnar and goblet cells. The findings of the present study support the view that the mucinous ovarian cystadenomas arise from the ovarian surface epithelium via a metaplastic process.