Abstract

One hundred and fourteen consecutive cases of histologically verified ovarian serous and mucinous tumors were reevaluated to clarify the histological specificity of borderline malignancy. The unique and definitive diagnostic criterion for the establishment of borderline malignancy of both serous and mucinous tumors is aggressive proliferation of lining cells without neighboring stromal invasiveness, but further reliable informations to suggest such low grade malignancy include less pleomorphic tumor cells with no apparent solid epithelial cell nest or secondary gland formation. Among various histological and cytological characteristics in relation to cellular pleomorphism, presence of one or more macronucleoli was very closely correlated with histological gradings of both tumors. True papillary growth with tendency of forming delicate secondary branching and marked epithelial stratification in serous tumors and the leakage of mucin into the adjacent stromal tissue in mucinous tumors were additional strong suggestions of invasive carcinoma, for which borderline malignancy should not be taken into consideration when some, but not all, of the above morphological features were detected.