Aberrant Cytokeratin 20 Reactivity in Epithelioid Malignant Mesothelioma: A Case Report

Our plain-English summary of Aberrant Cytokeratin 20 Reactivity in Epithelioid Malignant Mesothelioma: A Case Report, by R. Manur, I. Lamzabi (Applied Immunohistochemistry & Molecular Morphology, 2019).

The study

• Authors: R. Manur, I. Lamzabi
• Journal: Applied Immunohistochemistry & Molecular Morphology
• Published: 2019;27(10):e93-e96
• Type of article: Case report
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant mesothelioma is an uncommon neoplasm that should be distinguished from the more common pulmonary adenocarcinomas and other metastatic lesions. Although diagnosis is based on morphologic features, immunohistochemical stains such as Calretinin, WT-1, CK-5/6, D2-40, Ber-Ep4, and MOC-31 are routinely used. Other organ-specific immunohistochemical markers are used when metastases from unknown primary lesion is suspected clinically. Here, we report a case of pleural epithelioid malignant mesothelioma expressing CK20. A 68-year-old male presented to the Emergency Department with nonproductive cough and progressive shortness of breath. Chest x-ray showed a large left-sided pleural effusion. Metastasis from a gastrointestinal primary was clinically suspected. Cytopathologic examination of the pleural fluid demonstrated atypical cells singly and in clusters with round nuclei, prominent nucleoli, and dense cytoplasm. The cell block demonstrated single and clusters of atypical cells positive for calretinin, D2-40, WT-1, CK-5/6, and CK7. Ber-EP4, MOC-31, TTF-1, Napsin-A, and CDX-2 were negative. CK20 was diffusely positive. A diagnosis of atypical mesothelial proliferation with aberrant CK20 expression was made. A subsequent pleural biopsy demonstrated sheets of highly atypical cells that were diffusely and strongly positive for the mesothelial markers and CK20. Multiple studies have shown malignant mesotheliomas to lack CK20 reactivity. To our knowledge, this is the first case report of a diffuse and strong CK20-positive mesothelioma. Such aberrant expressions should be kept in mind when cases are histologically atypical or lack reactivity for multiple mesothelial markers, especially when a gastrointestinal primary malignancy is suspected.

In plain English

This case report describes one patient, a 68-year-old male nonsmoker who went to the emergency department with a dry cough and worsening shortness of breath. A chest x-ray showed a large fluid collection around the left lung. Scans showed nodules along the left pleura and two cysts in the pancreas, so doctors suspected cancer that had spread from the digestive tract. Laboratory stains on the drained fluid, and later on pleural biopsies, were positive for several markers of mesothelial cells. Unusually, they were also diffusely positive for CK20, a marker the authors noted multiple studies had found absent in mesothelioma. Several other markers, including CDX-2, were negative. The biopsy diagnosis was epithelioid malignant mesothelioma of the pleura. The authors stated that, to their knowledge, this was the first report of diffuse CK20-positive mesothelioma in recent years. They concluded that pathologists should be aware of this unusual staining to avoid misdiagnosis, especially when a digestive-tract cancer is suspected. The article did not report any asbestos exposure history, any treatment for the mesothelioma, or how the patient fared afterward.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (one patient)
• Who was studied: One 68-year-old male nonsmoker with a history including type II diabetes, chronic obstructive pulmonary disease, asthma and ulcerative colitis. The authors are from the Department of Pathology, Pennsylvania Hospital, Philadelphia. The year of diagnosis is not stated.
• Exposure: Not reported. The article gives no asbestos or occupational exposure history. It studies immunohistochemical staining (markers including CK20) in pleural fluid and biopsy samples.
• Main results:
  • Scans showed extensive left pleural nodularity and two cystic lesions in the head of the pancreas (1.3 and 2.9 cm). A primary cancer of the digestive tract was clinically suspected.
  • In the pleural fluid cell block, the atypical cells were positive for calretinin, D2-40, WT-1, CK-5/6, CK7 and CK20 (diffuse). They were negative for Ber-EP4, MOC-31, TTF-1, Napsin-A and CDX-2.
  • The fluid was diagnosed as 'atypical mesothelial proliferation' with aberrant CK20 staining, and a tissue biopsy was recommended.
  • In the pleural biopsies, the neoplastic cells were positive for CK20 (diffuse), Pan-CK, calretinin, WT-1 and D2-40, and negative for Ber-EP4, MOC-31 and S-100. A diagnosis of epithelioid malignant mesothelioma was made.
• The authors' conclusion: The authors considered this, to their knowledge, the first case report of diffuse CK20-positive malignant mesothelioma in recent years. They concluded that CK20 positivity found with different methods indicates a real finding rather than a procedural error. They said pathologists should keep such aberrant expression in mind to avoid misdiagnosis, especially when a gastrointestinal primary is under consideration or when cases are histologically atypical or lack reactivity for multiple mesothelial markers.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Epithelioid, Malignant Mesothelioma, Neoplasm, Adenocarcinoma, Calretinin, Wilms Tumor 1 (WT-1), Podoplanin (D2-40), Ber-EP4.

Related studies

• Expression of thrombomodulin, calretinin, cytokeratin 5/6, D2-40 and WT-1 in a series of primary carcinomas of the lung: an immunohistochemical study in comparison with epithelioid pleural mesothelioma — C.E. Comin, L. Novelli, et al. (2014)
• Value of the mesothelium-associated antibodies thrombomodulin, cytokeratin 5/6, calretinin, and CD44H in distinguishing epithelioid pleural mesothelioma from adenocarcinoma metastatic to the pleura — P.M. Cury, D.N. Butcher, et al. (2000)
• Diagnostic utility of immunohistochemistry in distinguishing between epithelioid pleural mesotheliomas and breast carcinomas: a comparative study — N.G. Ordóñez, A.A. Sahin (2014)
• Utility of HBME-1 immunostaining in serous effusions — V. Ascoli, C. Carnovale-Scalzo, et al. (1997)
• Hypodermal decidualized endometrioma with aberrant cytokeratin expression. A lesion mimicking malignancy — J.F. Val-Bernal, D. Val, et al. (2011)
• Cytokeratin 7 and cytokeratin 20 expression in epithelial neoplasms: a survey of 435 cases — P. Chu, E. Wu, et al. (2000)

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