Diagnostic and biological determinants in undifferentiated and poorly differentiated ovarian carcinomas

Six ovarian undifferentiated carcinomas (UCs) and 19 poorly differentiated serous (14 cases) and endometrioid (5 cases) carcinomas with areas of solid diffuse carcinomas have been considered for the study. Pathological findings were analyzed in conjunction with molecular analysis concerning the structure and expression of nm23-H1 gene. Differences in the frequency of loss of heterozigosity (LOH) of this gene have been observed between the two groups, UCs displaying lower percentage of LOH (1/5) as compared to poorly differentiated tumors (17/17). The remaining 3 cases (1 UC and 2 poorly differentiated carcinomas) were homozygotes, i.e., noninformative. UCs might occur as a consequence of cellular dedifferentiation, being at the end of the differentiation spectrum of epithelial ovarian tumors. Nevertheless, this study suggests that, in a fraction of cases, UCs could represent a distinct entity not involved in the malignant progression, associated with peculiar DNA anomalies, one possibly being that of the nm23-H1 deletion. In other words, a noticeable subset of UCs, not harboring nm23-H1 alterations, may be histologically uncommitted "ab initio". Moreover, nm23-H1 LOHs could be considered early events in the ovarian carcinogenesis, because similar molecular patterns were found both in primary and metastatic sites of the same tumor.