Prominent formation of papillae is noted lined by relatively bland mesothelial cells, and absence of mitoses. Invasion is absent. WDPM must also be distinguished from hyperplastic mesothelial processes. Papillary structures may occur in mesothelial hyperplasia but this degree of conspicuous papillary pattern, lack of inflammation and accompanying reactive changes in the adjacent serosal tissue also point to the diagnosis of WDPM. Image
The tumor shows a papillary architecture with branching coarse, paucicellular papillae lined by cuboidal cells. These lining cells stain for calretinin and keratin AE1/3 and are negative for CEA, consistent with their mesothelial origin.
The lining mesothelial cells focally contain subnuclear vacuoles, a described feature of this tumor. Nuclei also show central vesicular nuclei and are relatively bland overall.
Well-differentiated papillary mesothelioma of the peritoneum is a rare, enigmatic variant of mesothelioma possessing low malignant potential but requiring long-term surveillance. The majority are in the peritoneum in women of reproductive age with no history of asbestos exposure and in the tunica vaginalis of men.
WDPM of the peritoneum in women is frequently asymptomatic. When symptomatic, there may be abdominal pain, ascites, adnexal mass, and menorrhagia. Intraoperatively, single or multiple nodules involves the mesentery, omentum, and occasionally the ovarian surface. In a review, 57% had nodules <1.0 cm, 20% had 1 or more nodules between 1.0 and 3.0 cm, and the remaining 23% presented with at least 1 dominant mass >3.0 cm (Hoekstra). Tumor nodules were described as nodular in the majority, and the remaining as papillary, calcified, hemorrhagic, spiculated, cystic, or plaque-like.
WDPM of the peritoneum in women is often associated with an indolent course although there is some variability. Outcome is usually favorable after tumor-debulking surgery without adjuvant therapy. However, several WDPMs have pursued a more aggressive course, resulting in death.
Galateau-Sallé F, Vignaud JM, Burke L, Gibbs A, Brambilla E, Attanoos R, Goldberg M, Launoy .Well-differentiated papillary mesothelioma of the pleura: a series of 24 cases. Am J Surg Pathol. 2004 Apr;28(4):534-40.
Hoekstra AV, Riben MW, Frumovitz M, Liu J, Ramirez PT. Well-differentiated papillary mesothelioma of the peritoneum: a pathological analysis and review of the literature.Gynecol Oncol. 2005 Jul;98(1):161-7.