Epithelial noncarcinoid tumors and tumor-like lesions of the appendix. A clinicopathologic study of 184 patients with a multivariate analysis of prognostic factors.

BACKGROUND: The current understanding of appendiceal epithelial tumors is based on series composed of relatively small numbers of patients and on case reports. The aim of this study was to perform clinicopathologic correlation, particularly concerning prognosis, on a relatively large series of patients with epithelial tumors and tumor-like lesions of the human vermiform appendix.
METHODS: One hundred eighty-four cases of simple mucoceles, hyperplastic polyps, adenomas, carcinomas, and mucinous tumors of uncertain malignant potential (UMP) were reviewed. Retrospective follow-up data were obtained in carcinoma and UMP tumor cases.
RESULTS: Most neoplasms were of the mucinous type characteristic of the appendix, but a small fraction were nonmucinous and resembled neoplasms typical of the spectrum encountered in the colorectum. Both benign and malignant conditions in some cases showed acellular mucin dissecting the appendiceal wall and mucin outside the appendix. Immunostains were sometimes helpful in identifying epithelial cells within mucus, but hematoxylin and eosin and mucin stains were adequate in most cases. Two factors were significantly associated with survival by multivariate analysis: the presence of mucin outside the right lower quadrant of the abdomen and the presence of epithelial cells in the peritoneal cavity outside the appendix.
CONCLUSIONS: The distribution of mucin within the abdomen and the presence of cells outside the visceral peritoneum of the appendix are important prognostic factors that should be recorded in these neoplasms. Tumors designated as UMP lesions behave in a benign or low grade fashion.