5 - Peritoneal Washings

Abstract

Peritoneal washing cytology is used to identify microscopic spread of cancer not visible by gross inspection of the peritoneal surface. In some cancer patients, positive results are the only evidence of metastatic disease to the peritoneum. Because positive results correlate with poorer prognosis, cytologic findings are included in the staging system for ovarian and fallopian tube cancers. In some instances, peritoneal washing cytologic study is also used to detect peritoneal spread of nongynecologic malignancies such as gastric cancer. Because peritoneal washings are obtained as part of a cancer staging procedure, there is usually a concurrent histologic specimen, and representative slides from the histologic specimen can be helpful in a side-by-side comparison of a diagnostically difficult specimen. In a normal, benign peritoneal washing specimen, mesothelial cells are arranged predominantly in flat sheets, often large and occasionally folded, often accompanied by histiocytes. High-grade carcinomas are usually easy to recognize, whereas low-grade cancers and borderline tumors are challenging. Although peritoneal washing cytology is no longer part of the staging system for endometrial cancer, the International Federation of Gynecology and Obstetrics and the American Joint Committee on Cancer continue to recommend the collection of peritoneal washings in women with endometrial cancer because it may provide useful information for treatment decisions.