Ovarian mucinous cystadenocarcinoma with mural nodule of carcinomatous derivation. A light and electron microscopic study.

A case of an ovarian mucinous tumor with a mural nodule is reported. The epithelial elements consisted of benign, low malignant potential, and invasive mucinous carcinoma. The latter was present in one focus near the surface of the mural nodule as well as in some shallow depressed areas in the cyst wall. The nodule itself was made up of highly malignant, anaplastic cells which on light microscopic examination showed some similarities to the cells previously described in the sarcomatous and in some of the sarcoma-like mural nodules. However, analysis of light microscopic features in our case showed continuity and histologic similarities between the malignant mucinous cells and the sarcoma-appearing elements in the mural nodule. Ultrastructural features also supported an epithelial origin of the cells within the mural nodule. This case is the first of its kind with light and electronmicroscopic documentation and supports an epithelial origin for some of the mural nodules in ovarian mucinous tumors.