Sarcoma-like mural nodules combined with a microfocus of anaplastic carcinoma in mucinous ovarian tumor

A case of mucinous ovarian tumor with sarcoma-like mural nodules, one of which coexisted with a microfocus of anaplastic carcinoma, was studied by light, electron microscopic, and histochemical examinations. The case suggested that the formation of sarcoma-like mural nodules may be the result of the proliferation of undifferentiated mesenchymal cells which exist beneath the mucinous epithelium by some stimulation like hemorrhage in the cyst wall. Histologically, the mononucleated cells composing the sarcoma-like mural nodules had epithelioid characteristics, particularly at the areas where the covering mucinous epithelium had already detached. The case also suggested that the findings of epithelioid characteristics in the sarcoma-like mural nodules themselves do not imply these nodules to be anaplastic carcinoma, but merely an epithelioid differentiation from undifferentiated mesenchymal cells, namely one of reactive products. However, the existence of a microfocus of anaplastic carcinoma combined with the sarcoma-like mural nodule necessitates a careful histologic analysis of mural nodules for the treatment of patients and the determination of the prognosis.