Pleura & peritoneum

Pleura mesothelial tumors

Localized mesothelioma



Last author update: 11 January 2024
Last staff update: 16 January 2024

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PubMed Search: Localized mesothelioma

Yin P. (Rex) Hung, M.D., Ph.D.
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Cite this page: Hung YP. Localized mesothelioma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/pleuralocmalmesothelioma.html. Accessed February 22nd, 2024.
Definition / general
  • Localized mesothelioma is a rare malignant mesothelial tumor that is microscopically identical to diffuse mesothelioma
  • Unlike diffuse mesothelioma, localized mesothelioma is solitary and circumscribed, with no radiologic, intraoperative, gross or microscopic evidence of diffuse serosal involvement
Essential features
  • Solitary and circumscribed, with no radiologic, intraoperative, gross or microscopic evidence of diffuse serosal involvement
  • Microscopically identical to diffuse pleural mesothelioma
  • Can be subclassified into epithelioid, biphasic and sarcomatoid histotypes
  • Mesothelial immunophenotype
Terminology
  • Not recommended: localized malignant mesothelioma
  • Not recommended: solitary malignant mesothelioma
ICD coding
  • ICD-O: 9050/3 - mesothelioma, malignant
  • ICD-10: C45.0 - mesothelioma of pleura
  • ICD-11: 2C26.0 - mesothelioma of pleura
Epidemiology
Sites
Pathophysiology
  • Unknown at this time
Etiology
Clinical features
Diagnosis
  • Diagnosis of localized mesothelioma cannot be rendered based on the histologic findings alone and requires correlation with clinical and radiologic findings, in order to ascertain that the tumor is solitary and circumscribed, with no evidence of diffuse serosal involvement
Radiology description
Radiology images

Images hosted on other servers:
CT chest imaging

CT chest imaging

Prognostic factors
Case reports
Treatment
Clinical images

Images hosted on other servers:
Intraoperative view

Intraoperative view

Gross description
  • Circumscribed; can be encapsulated or nonencapsulated
  • Tumor size ranging from < 2 cm to ~ 20 cm (Mod Pathol 2020;33:281)
Gross images

Images hosted on other servers:
Circumscribed mass Circumscribed mass

Circumscribed mass

Microscopic (histologic) description
  • Histologically identical to diffuse mesothelioma
  • Comprises epithelioid, biphasic and sarcomatoid histologic types
Microscopic (histologic) images

Contributed by Yin P. (Rex) Hung, M.D., Ph.D.
Epithelioid cells Epithelioid cells

Epithelioid cells

CK7

CK7

WT1

WT1

Calretinin

Calretinin

D2-40

D2-40

Positive stains
Negative stains
Molecular / cytogenetics description
  • Genomically heterogeneous with multiple subgroups (Mod Pathol 2020;33:271)
    • Alterations involving BAP1, CDKN2A or NF2
    • Mutations involving TRAF7
    • Genomic near haploidization, with extensive loss of heterozygosity involving most chromosomes except chromosomes 5 and 7
Molecular / cytogenetics images

Images hosted on other servers:
Copy number alterations

Copy number alterations

Karyotype

Sample pathology report
  • Pleura, pleurectomy:
    • Localized pleural biphasic mesothelioma (see comment)
    • Comment: Radiologic findings and intraoperative findings were reviewed. Radiologically, intraoperatively and grossly, this tumor is solitary and circumscribed. Microscopically, it is biphasic, with ~70% epithelioid component and ~30% sarcomatoid component. By immunohistochemistry, the tumor cells in both components are positive for AE1 / AE3 keratins, WT1, calretinin and D2-40 (patchy) and are negative for TTF1, MOC31 and claudin4, with complete loss of BAP1 nuclear staining, supporting the above diagnosis. Resection margin is negative for tumor. Tumor is 0.2 cm from the resection margin.
Differential diagnosis
Board review style question #1

Which of the following statements is true about localized mesothelioma?

  1. It involves only the pleura
  2. Its histopathologic features are identical to those of diffuse mesothelioma
  3. Loss of BAP1 nuclear staining is present in all cases
  4. Radiologic and intraoperative correlation is not needed to render this diagnosis
Board review style answer #1
B. Its histopathologic features are identical to those of diffuse mesothelioma. As such, its diagnosis requires correlation with radiologic, intraoperative and gross findings to ascertain that the tumor is indeed solitary with no diffuse serosal involvement. Answer D is incorrect because radiologic and intraoperative correlation is needed to render the diagnosis of localized mesothelioma. Answer A is incorrect because localized mesothelioma can involve the pleura and other serosal membranes including the peritoneum. Answer C is incorrect because the loss of BAP1 nuclear staining is seen in only a subset of localized mesotheliomas.

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Reference: Localized mesothelioma
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