Special Considerations for Peritoneal Washings

Peritoneal washings (PW) can present frustrating dilemmas for the cytologist due to the prevalence, predominately in women, of benign proliferative processes of Mullerian, mesonephric, and mesothelial origin that may occur. In most instances, peritoneal washings or lavage are performed to screen for the presence of tumor cells in the peritoneal cavity and are performed in association with a surgical procedure. The goal of this assessment is not a primary cytologic diagnosis, but to confirm the presence or absence of tumor cells at that site, which makes comparison with the surgical specimen paramount. This chapter outlines an approach to these specimens, discusses commonly and uncommonly encountered entities along with their differential diagnoses and immunoprofiles, and provides numerous sample reports.