Peritoneum, omentum and mesentery
Mesothelial lesions
Epithelioid mesothelioma

Author: Aysha Mubeen, M.D. (see Authors page)
Editor: Raul S. Gonzalez, M.D.

Revised: 15 May 2018, last major update February 2018

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: Peritoneum epithelioid mesothelioma
Cite this page: Mubeen, A. Epithelioid mesothelioma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/peritoneummesothelioma.html. Accessed May 24th, 2018.
Definition / general
  • Mesothelioma is a neoplasm arising from mesothelial cells that line serous cavities, such as the pleura and peritoneum
  • Pleural mesothelioma is much more common than peritoneal mesothelioma
  • Epithelioid mesothelioma is the most frequent histologic type of malignant mesothelioma; sarcomatoid and biphasic subtypes are less common
  • 20-33% of malignant mesothelioma arises in the peritoneum (Semin Oncol 2002;29:51)
Essential features
  • Myxoid variant of peritoneal epithelioid mesothelioma is a rare entity (only 5 cases reported in the literature)
    • Dyscohesive epithelioid cells in a myxoid background
    • Can raise diagnostic difficulty in differentiating from other myxoid lesions of the peritoneum (e.g. adenocarcinoma)
    • Panel of immunohistochemical markers is generally required to reach the correct diagnosis
Epidemiology
  • Mesothelioma is often due to asbestos exposure, whether in the pleura, peritoneum and pericardium; cumulative asbestos exposure is directly proportional to risk of cancer (J Med Case Rep 2008;2:121)
Pathophysiology
  • Asbestos fibers lead to chronic inflammation, which causes the release of free radicals
  • Latent period between asbestos exposure and disease averages 20 - 30 years (Cancer Treat Rev 2012;38:605)
Clinical features
  • Patients with mesothelioma do not present with distinctive symptoms, causing difficulties in diagnosis and treatment
  • When symptomatic, usually present with abdominal pain, ascites and abdominal distention
  • Prognosis is poor
Prognostic factors
Case reports
  • 44 year old woman with extensive myxoid change in well differentiated papillary mesothelioma of the pelvic peritoneum (Ann Diagn Pathol 2002;6:164)
  • 59 year old man with abdominal bloating and vague abdominal pain (Case of the Week #441)
  • 60 year old woman with myxoid variant of peritoneal epithelioid malignant mesothelioma (Cesk Patol 2014;50:149)
Treatment
  • Systemic chemotherapy, cytoreductive and palliative surgery
Gross description
  • For omental myxoid tumors, omentum resection shows replacement by a gelatinous tumor
Microscopic (histologic) description
  • Myxoid variant:
    • Tumor consists of dyscohesive medium to large epithelioid cells with a moderate to abundant amount of eosinophilic cytoplasm dispersed in a myxoid background
    • Some of the tumor cells can show intracytoplasmic clear vacuoles
    • Nuclei show coarse chromatin with prominent nucleoli
    • Mitotic figures are usually inconspicuous
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Aysha Mubeen, M.D. (epithelioid mesothelioma):

Various images



Myxoid variant of epithelioid mesothelioma:

4x

10x

10x

40x


2x

4x

40x

Calretinin

MOC31

Virtual slides

Images hosted on other servers:

Epithelioid mesothelioma: 70 year old man with pleural effusion

Cytology description
  • Clusters of epithelioid cells (morulae) with knobby contour
  • Abundant cytoplasm, round nuclei and prominent nucleoli
  • Mild atypia
Cytology images

Images hosted on PathOut server:

Contributed by Aysha Mubeen, M.D. (myxoid variant):

Cell block

ThinPrep

Diff-Quik

Positive stains
Negative stains
Electron microscopy description
  • Very long, thin apical microvilli and the absence of glycocalyx (compare with adenocarcinoma, which has shorter villi)
Electron microscopy images

Images hosted on other servers:

Various images

Differential diagnosis
Additional references
Board review question #1
Which of the following stains is positive in the myxoid variant of epithelioid mesothelioma and helps to differentiate it from mucinous adenocarcinoma?

  1. B72.3
  2. Claudin4
  3. D2-40
  4. MOC31
Board review answer #1
C. D2-40