Organizing Mucinous Ascitis Masquerading as Pseudomyxoma Peritonei: A Process Possibly Caused by Metaplasia But Not Neoplasia

Mucinous ascitis can be differentiated from the more ominous condition pseudomyxoma peritonei microscopically by the absence of epithelial cells amidst mucin pools in the former. Herein we communicate a brief report of organizing mucinous ascitis in a 34-year-old woman, with recurrent abdominal pain localized to right iliac fossa. Imaging studies were suggestive of mucocele. Conservative management, followed by appendicectomy and enbloc removal of the surrounding mucinous adhesions, was performed. Histopathology revealed chronic obliterative appendicitis, along with presence of mucin pools, mixed inflammatory cells and reactive mesothelial cells in the surrounding peri-appendiceal tissue. There was an absence of morphologically well-defined, neoplastic epithelial cells in the mucinous pool, thus excluding the diagnosis of pseudomyxoma peritonei. The problem of reactive mesothelial cells, which at places look like epithelial cells, was solved by a panel of immunohistochemistry. The localized mucinous ascitis possibly have originated from the mucinous metaplasia of the mesothelial lining cells of the peritoneum, secondary to recurrent attacks of appendicitis.