Re: annual report to the nation on the status of cancer (1973 through 1998), featuring cancer with recent increasing trends.

I read with interest the special article by Howe et al. (1). A 14.5% annual increase in peritoneal cancer was observed from 1992 through 1998. Peritoneal cancer was first described by Smerdlow (2) in 1959 and has since been referred to by various terms, including multifocal extra-ovarian carcinoma, serous surface papillary carcinoma, primary carcinoma of the peritoneum, and carcinoma of the coelomic epithelium. In the early 1990s, there was an increased recognition of peritoneal cancer as a distinct entity. In 1994, the Pathology Committee of the Gynecologic Oncology Group (GOG) established a definition of peritoneal carcinoma as a tumor with 5.0 mm or less of ovarian stromal invasion. This definition has been subsequently utilized in all GOG studies, which are conducted in more than 100 major teaching institutions and hospitals in the United States. It is likely that establishing this uniform definition has shifted cases formerly classified as ovarian cancer to peritoneal cancer. In view of the fact that ovarian carcinoma and peritoneal carcinoma are identical in histology, biology, response to therapy, and prognosis, the GOG has included both ovarian and peritoneal cancer patients in their studies since 1996. Given the changing nomenclature, studies evaluating population incidence trends in gynecologic cancers should also combine ovarian and peritoneal carcinomas.