Pseudomyxoma peritonei and malignant mucocele of the appendix. A case report.

A case of pseudomyxoma peritonei originating in a malignant mucocele of the appendix, a very rare clinical entity, is presented. The cytologic findings in the gelatinous ascitic fluid of epithelial clusters with minimal nuclear atypia suggested a diagnosis of pseudomyxoma peritonei. Both routine stains and special stains for mucus assisted in making the cytologic diagnosis. Histologic examination of the laparotomy specimen confirmed the presence of a well-differentiated mucinous cystadenocarcinoma, with an apparent appendiceal origin. The origins and relationships of appendiceal mucocele and pseudomyxoma peritonei are discussed.