Pseudomyxoma peritonei, peritoneal mucinous carcinomatosis of presumed appendiceal origin.
This case illustrates the diagnostically elusive nature of the clinical syndrome of pseudomyxoma peritonei. Pseudomyxoma peritonei is a rare clinical condition characterized by progressive abdominal distention by intraperitoneal accumulation of mucus (i.e. mucinous ascites). The mucinous ascites in pseudomyxoma peritonei has been attributed to both high grade and low grade malignancies. The primary tumor in pseudomyxoma is most commonly considered to be appendiceal or ovarian in origin, but other primary sites, including colonic, are sometimes considered most likely. It is sometimes difficult to know with any confidence what the primary site is. Immunohistochemical staining patterns commonly make the appendix most likely, but there is no immunostain specific for the appendix.
Examination of appendiceal mucosal lesions has shown that mucus-forming lesions range from relatively benign mucosal hyperplasia, to mucinous cystadenomas, to mucinous cystadenocarcinomas. Although each lesion produces mucin, the ability to produce pseudomyxoma peritonei is limited to those which penetrate through the appendiceal wall by either tumor cell invasion or appendiceal wall breakage, with resultant intraperitoneal spread of mucin-producing tumor cells. Microscopic examination of the lesion in this case demonstrates poorly differentiated cells, many with signet ring features, within pools of mucin.
Patients with pseudomyxoma peritonei may present with a variety of vague abdominal complaints related to the location of intraperitoneal mucin-producing tumor implants. This phenomenon has attributed to a "redistribution phenomenon," which describes spread of tumor within the abdominal cavity at predictable anatomic sites. Autopsy gross examination of the patient in this case demonstrated extensive intraperitoneal involvement and an omental cake (clinically attributed to splenomegaly). The anatomy around the primary source, which was most likely the appendix in this case, was distorted to the point where identification of the appendix was difficult. Complaints such as abdominal pain or nausea may wax and wane, resulting in a delay in diagnosis or even misdiagnosis. Patients in advanced stages of pseudomyxoma peritonei develop abdominal distention with mucinous ascites, termed "jelly belly." The patient in this case did have abdominal ascites, but the ascites was serous and attributed to alcoholic cirrhosis.
Ultimately, as in this case, patients with pseudomyxoma peritonei develop intestinal obstruction and related complications, which may fatal. This case demonstrates the retrospective educational utility of autopsy in examining the natural history of a patient's death. Making the diagnosis of pseudomyxoma peritonei at the time this patient first presented would not have saved his life, but the case was presented at a critical care medicine quality assurance conference and in the patient safety committee, generating vigorous discussion and ideas about how this diagnosis might be made earlier in similar cases in the future, allowing life-prolonging therapy.
Contributed by Timothy S Gorrill, MD and Larry Nichols, MD