A 46-year-old man with no significant past medical history presented for evaluation of worsening ascites. He was a Mexican immigrant who came to the United States in 2000 with no known exposure to contacts with tuberculosis. He reported first having ascites 2 years prior to admission. He had undergone therapeutic paracentesis 3 times at an outside hospital, most recently 1 month prior to presentation at our institution. Evaluation at an outside facility did not determine a cause of ascites and was negative for hepatic and cardiac etiologies. He denied abdominal pain or fevers. History was positive for early satiety, nausea, and muscle wasting. He reported significant alcohol use and was a daily smoker.
Review of outside hospital records was significant for a laparoscopic appendectomy for a perforated appendix and ascites 6 months prior. The surgical report described an acutely inflamed appendix, 4 L of turbid ascites, and what appeared to be frank peritonitis, which obscured the abdominal viscera. The pathology report described the external surface of the appendix as roughened and granular in appearance, with a diagnosis of acute appendicitis with perforation. No appendiceal neoplasm was observed.
Physical exam revealed cachexia with significant muscle wasting, abdominal distention, and positive fluid wave. Laboratory values demonstrated normal liver chemistries, alkaline phosphatase 164 IU/L, and platelet count 727,000/muL. Tumor markers including alpha-fetoprotein, CA125, CA19-9, and carcinoembryonic antigen were within normal limits.
Computed tomography (CT) of the abdomen and pelvis revealed loculated abdominal ascites with nodular thickening of some of the septations (Figure 1). There was no evidence of cirrhosis or splenomegaly. An eccentric soft-tissue density along the surface of the distal transverse colon measuring 2.6 x 2.0 cm was noted. Paracentesis removed 7.5 L of mucinous, jelly-like fluid notable for white blood cells 680/muL, polymorphonuclear leukocytes 204/muL, red blood cells 925/muL, lymphocytes 30%, and monocytes of 40% (Figure 2). Cytology was negative for malignant cells but did show abundant mucus. Biochemical analysis of the fluid could not be performed due to its mucinous nature. Cultures and gram stain of the fluid, including examination for acid-fast bacilli, were negative.
Colonoscopy was required due to transverse colon thickening on CT of the abdomen and pelvis, and this revealed a 20-mm submucosal nodule in the transverse colon (Figure 3). Several bite-on-bite biopsies were taken with cold forceps. Histologic examination revealed an infiltrative population of discohesive plasmacytoid cells involving the muscularis mucosa and the submucosa. Immunohistochemical studies demonstrated expression of AE1/AE3, CK7, calretinin, WT1, and D2-40. There was no significant reactivity for CK20, BerEp4, MOC31, PAX8, chromogranin, or CDX2 (Figure 4). Given the clinical, radiographic, and histologic findings of infiltrative mesothelial cells, a diagnosis of malignant peritoneal mesothelioma, epithelioid-type, was made. Surgical debulking as well as hyperthermic intraperitoneal chemotherapy were recommended by colorectal surgery and medical oncology. However, because this treatment is not available at our center, the patient was discharged with plans to follow up at another center. No further follow-up is available.