Intermediate filament expression in mesotheliomas: leiomyoid mesotheliomas are not uncommon

Our plain-English summary of Intermediate filament expression in mesotheliomas: leiomyoid mesotheliomas are not uncommon, by F.G. Mayall, H. Goddard, A.R. Gibbs (Histopathology, 1992).

The study

• Authors: F.G. Mayall, H. Goddard, A.R. Gibbs
• Journal: Histopathology
• Published: 1992;21(5):453-7
• Cited by: 40 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In this study we examined intermediate filament expression in 45 formalin-fixed mesotheliomas. Immunostaining for cytokeratin was found in 86%, for vimentin in 71%, and for desmin in 4%; none stained for glial fibrillary acidic protein or neurofilament. The two biphasic mesotheliomas which expressed desmin also expressed smooth muscle actin but were negative for myoglobin. This, together with the ultrastructural findings, was taken as unequivocal evidence of a leiomyoid form of mesothelioma which might easily be confused with leiomyosarcoma. Both of these tumours co-expressed cytokeratin, exemplifying the value of cytokeratin immunostaining in the distinction between mesothelioma and sarcoma. Consistent non-expression of glial fibrillary acidic protein in mesotheliomas may help to distinguish them from nerve sheath tumours.

In plain English

This laboratory study from Penarth and Cardiff, UK, examined stored tissue from 45 mesotheliomas (13 epithelial, 19 biphasic, 13 sarcomatous). The authors stained the tissue for five cell-structure proteins called intermediate filaments. Cytokeratin was found in 86% of tumours, vimentin in 71% and desmin in 4%. None stained for glial fibrillary acidic protein (GFAP) or neurofilament. The two desmin-positive tumours were both biphasic. They also stained for smooth muscle actin but not myoglobin, and both expressed cytokeratin. Electron microscopy of one showed smooth-muscle-type features. Both patients were elderly men with a putative history of asbestos exposure. Lung fibre analysis found 2.8 million crocidolite fibres per gram of dried lung in one. The other had 0.9 million, which the authors said is within their laboratory's range for unexposed people. Both died within 1.5 years of diagnosis. The authors concluded that a smooth-muscle-like (leiomyoid) form of mesothelioma exists that could be mistaken for leiomyosarcoma. They added that cytokeratin staining helps distinguish mesothelioma from sarcoma, and that absent GFAP staining may help distinguish mesotheliomas from nerve sheath tumours.

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: Laboratory immunohistochemical study of archived tumour tissue (case series of pathology specimens), with electron microscopy and lung fibre analysis for two unusual cases
• Who was studied: 45 mesotheliomas from autopsy and surgical material (13 epithelial, 19 biphasic, 13 sarcomatous), studied at Llandough Hospital, Penarth, and the University of Wales College of Medicine, Cardiff, UK. Dates of the cases are not given, and tumour site (pleural or peritoneal) is not stated.
• Exposure: The study examined tumour staining patterns, not asbestos exposure. For the two desmin-positive cases only, the authors reported a putative history of asbestos exposure and lung crocidolite fibre counts.
• Main results:
  • Across all 45 mesotheliomas, cytokeratin staining was found in 86%, vimentin in 71% and desmin in 4%. None stained for glial fibrillary acidic protein or neurofilament.
  • By subtype (Table 2), cytokeratin and vimentin rates were: epithelial 92% and 54%; biphasic 100% and 74%; sarcomatous 61% and 87%. Cytokeratin staining was less common in sarcomatous tumours, and vimentin was the reverse. Desmin was found only in biphasic tumours (10%).
  • The two desmin-positive tumours, both biphasic, showed a similar staining pattern for smooth muscle actin, but myoglobin was not found. Both expressed cytokeratin in their epithelial and stromal components.
  • Electron microscopy was available for one of the two tumours. It showed evidence of leiomyoid (smooth muscle) differentiation in many of the stromal cells.
  • One of the two desmin-positive cases had a lung crocidolite count of 2.8 x 10^6 fibres per gram of dried lung.
  • The other desmin-positive case had a crocidolite count of 0.9 x 10^6 fibres per gram of dried lung, which the authors said is within the laboratory range for unexposed individuals (up to 1 x 10^6). There was no increase in other amphiboles.
  • Both patients with desmin-positive mesothelioma died within 1.5 years of diagnosis.
• The authors' conclusion: The authors concluded that the findings were unequivocal evidence of a leiomyoid form of mesothelioma that could easily be confused with leiomyosarcoma. They suggested it accounts for approximately 4% of mesotheliomas. They also said cytokeratin staining aids in telling mesothelioma from sarcoma, and that consistent absence of GFAP may help distinguish mesotheliomas from nerve sheath tumours.
• Limitations the authors state:
  • The tissue used for electron microscopy was suboptimally preserved.
  • The authors acknowledged that other researchers have reported cytokeratin expression in smooth muscle tumours. This is a caveat to using cytokeratin to tell the two apart.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Desmin, Biphasic Mesothelioma, Sarcoma.

Related studies

• Use of intermediate filament antibodies in the differential diagnosis of gynecological neoplasia — F.C. Ramaekers, J.J. Puts, et al. (1985)
• Cytokeratin 7 and cytokeratin 20 expression in epithelial neoplasms: a survey of 435 cases — P. Chu, E. Wu, et al. (2000)
• Keratins 7 and 20 as diagnostic markers of carcinomas metastatic to the ovary — C.C. Wauters, F. Smedts, et al. (1995)
• Comparative proteomic analysis of malignant pleural mesothelioma evidences an altered expression of nuclear lamin and filament-related proteins — L. Giusti, Y. Da Valle, et al. (2014)
• Leiomyoid mesotheliomas — H. Battifora (1993)
• Reactive and neoplastic serosal tissue. A light-microscopic, ultrastructural, and immunocytochemical study — J.W. Bolen, S.P. Hammar, et al. (1986)

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