Peritoneum, omentum and mesentery
Mesothelial lesions
Peritoneal malignant mesothelioma


Topic Completed: 23 May 2019

Revised: 23 May 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Peritoneal malignant mesothelioma[title]
Page views in 2019 to date: 284
Cite this page: Hung Y. Peritoneal malignant mesothelioma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/peritoneummesotheliomageneral.html. Accessed June 15th, 2019.
Definition / general
  • Tumor that originates from the serosal lining of the peritoneal cavity
Essential features
  • Peritoneal malignant mesothelioma shows weaker association with asbestos exposure and more likely involves women / young patients than pleural malignant mesothelioma
  • Histologic variants (epithelioid, biphasic and sarcomatoid) impart prognostic information with treatment implications
  • Loss of BAP1 expression is seen in 40 - 60% of peritoneal malignant mesothelioma, not sensitive but fairly specific for the diagnosis of malignant mesothelioma in the appropriate histologic context
Terminology
  • Peritoneal mesothelioma
  • Malignant peritoneal mesothelioma
  • Diffuse malignant peritoneal mesothelioma
  • Abdominal mesothelioma
ICD coding
    ICD-10:
  • C45.1 - mesothelioma of peritoneum

    ICD-0:
  • 9050/3 - malignant mesothelioma
  • 9051/3 - sarcomatoid / desmoplastic malignant mesothelioma
  • 9052/3 - epithelioid malignant mesothelioma
  • 9053/3 - biphasic malignant mesothelioma
Epidemiology
Sites
  • Involves the serosal lining in the peritoneal cavity, often of multiple intra-abdominal organs
  • Generally diffuse, rarely solitary / localized (Am J Surg Pathol 2005;29:866)
Etiology
Clinical features
  • More likely to affect women and young patients as compared to pleural malignant mesothelioma (Cancer Causes Control 2009;20:935)
  • Symptoms can be nonspecific and depend on the extent of involvement
  • Presentation includes most commonly abdominal pain, distension or ascites; rarely incidental or with new hernia, bowel obstruction or perforation (Tumori 2003;89:269, Ann Gastroenterol 2018;31:659)
  • Morbidity / mortality primarily due to locoregional spread with extra-abdominal metastasis rare
  • Median overall survival of 3 - 7 years with a 5 year survival rate of 40 - 60% with treatment (Ann Gastroenterol 2018;31:659)
Diagnosis
  • Radiologic assessment of disease extent by computed tomography (CT) or magnetic resonance imaging (MRI)
  • Cytologic analysis of peritoneal fluid, though this is not entirely sensitive
  • Definitive diagnosis is most commonly based on histologic analysis of surgical specimen from laparoscopic / open or core needle biopsy
  • Peritoneal malignant mesothelioma, particularly the sarcomatoid variant, is difficult to diagnose and requires multiple immunohistochemical markers to exclude mimics
  • Since no single immunohistochemical marker is entirely sensitive and specific for the diagnosis, a panel of at least 2 positive markers and 2 negative markers is recommended (Hum Pathol 2017;67:160)
Radiology description
  • Multiple nodular lesions involving omentum and the mesentery, peritoneal thickening and accumulation of ascites (Anticancer Res 2016;36:1067)
Radiology images

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Omental caking

Prognostic factors
Case reports
Treatment
  • Cytoreductive surgery, often combined with hyperthermic intraoperative chemotherapy, generally recommended for treating epithelioid variant (and some biphasic) but not sarcomatoid variant (Ann Surg Oncol 2015;22:1686, Ann Surg Oncol 2018;25:667)
  • Chemotherapy types: hyperthermic intraoperative chemotherapy (HIPEC), early postoperative intraperitoneal chemotherapy (EPIC), long term intraperitoneal (IP) chemotherapy and systemic chemotherapy (Eur J Cancer 2016;65:69, Eur J Surg Oncol 2017;43:1228)
  • Radiation
  • Immunotherapy: clinical trial on using tremelimumab (anti-CTLA4 monoclonal antibody) and durvalumab (PD-L1 blockade) ongoing (Lancet Respir Med 2018;6:451)
Gross description
  • Multiple omental / serosal nodules and thickened peritoneum
Gross images

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Adhesion of abdominal organs

Microscopic (histologic) description
  • Unequivocal indicator of malignancy: invasion into adipose tissue or stromal invasion (Am J Surg Pathol 2000;24:1183, Arch Pathol Lab Med 2018;142:89)
  • Histologically classified into epithelioid, biphasic and sarcomatoid variants with implications on prognosis and treatment planning
  • Epithelioid mesothelioma is characterized by epithelioid to round tumor cells, which are often more monotonous than what are seen in most carcinomas
  • Sarcomatoid mesothelioma is characterized by spindled tumor cells
  • Biphasic mesothelioma is characterized by the presence of both epithelioid and sarcomatoid components, each comprising at least 10% of the tumor
  • In epithelioid mesothelioma, architectural / cytologic features that can be seen are diverse; histologic patterns most commonly seen are tubular, papillary and solid and more rarely micropapillary, trabecular, acinar, adenomatoid-like, clear cell, deciduoid, adenoid cystic-like, signet ring cell, small cell and rhabdoid (Arch Pathol Lab Med 2013;137:647)
  • In sarcomatoid mesothelioma, histologic patterns include conventional, desmoplastic, lymphohistiocytoid and those with heterologous differentiation (Arch Pathol Lab Med 2013;137:647, Am J Surg Pathol 2015;39:1568)
Microscopic (histologic) images

Contributed by Yin P. Hung, M.D., Ph.D.
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Epithelioid variant, solid growth

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Calretinin

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WT1

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Epithelioid variant, infiltrative growth

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Typically uniform tumor cells


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AE1 / AE3

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Calretinin

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WT1

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Biphasic variant

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AE1 / AE3

Cytology description
  • Large clusters to sheets of fairly monotonous mesothelial tumor cells
  • Limitation of cytologic diagnosis: rarely definitive, since tissue invasion is difficult to assess
Positive stains
Negative stains
Electron microscopy description
  • Microvilli and desmosomes
Molecular / cytogenetics description
Sample pathology report
  • Peritoneum and omentum, resection:
    • Malignant mesothelioma, epithelioid variant, 5.0 cm in greatest dimension
    • Surgical margins, negative for tumor
    • Comment: The tumor cells are positive for WT1, calretinin and D2-40, and are negative for claudin4, PAX8, MOC31 and CEA.
Differential diagnosis
  • Metastatic adenocarcinoma
    • Variable histologic overlap
    • Typically expresses other epithelial markers: claudin4, BerEP4, polyclonal CEA, MOC31 and B72.3
    • Rarely express keratin 5 / 6 and mesothelial markers (calretinin and D2-40), though WT1 is commonly expressed in carcinomas of Müllerian primary and CAIX is expressed in renal cell carcinoma, clear cell type
    • Expression of PAX8 favors renal or gynecologic origin and TTF1 favors lung origin
  • Sclerosing peritonitis
    • Reactive proliferation of stromal myofibroblasts, often associated with adjacent linear arrangement of mesothelial cells, chronic inflammation, surface fibrin deposition and occasionally entrapped fat
    • Associated with various conditions including luteinized thecomas (Am J Surg Pathol 1994;18:1)
    • Distinction can be challenging, particularly in small biopsies, cases with tangential sectioning or fat entrapment (Am J Surg Pathol 2000;24:1183)
  • Well differentiated papillary mesothelioma
  • Adenomatoid tumor of genital type
    • Benign mesothelial tumor that arises mostly commonly near the genital tract
    • Histology: a microcystic low power appearance with poor margination and tubules / cords of epithelioid cells with characteristic cytoplasmic vacuolation
    • Associated with immunosuppressive state in some cases (Histopathology 2018;73:1013)
    • Recurrent mutations in TRAF7 (Mod Pathol 2018;31:660)
  • Multicystic peritoneal inclusion cyst
    • Also known as multilocular inclusion cyst
    • Histology: multiple cysts of various sizes, each with thin fibrous walls lined by flattened mesothelial cells (Cancer 1989;64:1336)
    • TNS3-MAP3K3 or ZFPM2-ELF5 gene fusion in rare cases (Cancer Lett 2015;357:502)
  • Epithelioid hemangioendothelioma
Board review question #1
    Which of the following is true regarding peritoneal malignant mesothelioma?

  1. All cases are associated with asbestos exposure
  2. Compared to pleural mesothelioma, peritoneal mesothelioma more likely involves women and children
  3. Copy number loss of CDKN2A and NF2 is detected in all cases
  4. Histologic subtyping has no prognostic value
  5. The presence of intact BAP1 protein expression rules out malignancy entirely
Board review answer #1
B. Compared to pleural mesothelioma, peritoneal mesothelioma more likely involves women and children

Comment Here

Reference: Peritoneal malignant mesothelioma
Board review question #2
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    Which of the following is true regarding the two images (the tumor and the corresponding BAP1 immunostain) illustrated?

  1. This indicates germline BAP1 mutation(s) in all cases
  2. This is a metastatic adenocarcinoma
  3. This is a reactive mesothelial proliferation
  4. This is a sarcomatoid malignant mesothelioma
  5. This is an epithelioid malignant mesothelioma
Board review answer #2
E. This is an epithelioid malignant mesothelioma

Comment Here

Reference: Peritoneal malignant mesothelioma
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