The behavior of serous tumors of low malignant potential: are they ever malignant?

Although the literature describing the clinicopathologic features of serous borderline or low malignant potential (LMP) tumors of the ovary is extensive, the behavior of these neoplasms is not well understood. While some studies indicate a 30 to 40% mortality for advanced stage tumors, it is not clear whether this poor outcome is related to "benign" complications of the disease, such as bowel obstruction from adhesions, or to development of carcinomatosis from malignant transformation. In an effort to determine more clearly the cause of death of patients with serous LMP tumors and to assess the malignant potential of these tumors, defined by progression to invasive serous carcinoma, we reviewed 22 series, totalling 953 patients. Analysis of these studies reveals that for patients with stage I tumors, survival is 99%. For advanced stage disease, survival is 92%. Advanced-stage tumors associated with so-called invasive implants were excluded from this analysis because they were considered invasive serous carcinomas at the time of diagnosis rather than noninvasive LMP tumors. Various causes of death in patients with advanced-stage tumors include complications of the disease, complications of therapy, and, rarely, malignant transformation. Our review of 953 cases disclosed only seven (0.7%) tumors that appeared to have undergone malignant transformation, resulting in death from intraabdominal carcinomatosis. Because the rate of malignant transformation is exceedingly low and because classifying these tumors as malignant often leads to unnecessary treatment, we believe that the term low malignant potential or borderline tumor is not justified.(ABSTRACT TRUNCATED AT 250 WORDS)