Diffuse epithelial mesothelioma: a review of the ultrastructural spectrum

Our plain-English summary of Diffuse epithelial mesothelioma: a review of the ultrastructural spectrum, by I. Dardick, M. Jabi, W.T. McCaughey, et al (Ultrastructural Pathology, 1987).

The study

• Authors: I. Dardick, M. Jabi, W.T. McCaughey, S. Deodhare, A.W. van Nostrand, J.R. Srigley
• Journal: Ultrastructural Pathology
• Published: 1987;11(5-6):503-33
• Type of article: Case report, Review
• Cited by: 64 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Traditionally, diffuse epithelial mesotheliomas are mainly identified at the ultrastructural level by the numerous, long, wavy-appearing surface microvilli. By electron microscopy of a series of diffuse mesotheliomas of varying subtype (epithelial, biphasic, sarcomatous, and poorly differentiated), it can be demonstrated that the differentiation of this specialized surface organelle is quite variable even in well-differentiated lesions. The presence of only a few, scattered, short microvilli does not exclude a diagnosis of epithelial mesothelioma, particularly if historical, surgical, and radiologic findings support this diagnostic conclusion. Indeed, even the complete absence of surface microvilli is compatible with a diagnosis of diffuse epithelial mesothelioma. It is important to become aware of the spectrum of tumor cell differentiation in serosal tumors, as all of the fine structural diagnostic criteria in mesotheliomas are expressed to varying degrees in individual cases.

In plain English

This article was a pathologists' review of how diffuse mesothelioma looks under the electron microscope. The authors based it on their own electron microscope study of 70 tumors of the body's lining membranes (serosal tumors), 56 of them diffuse epithelial mesotheliomas. They chose 11 cases to show the range of appearances across the epithelial, biphasic, sarcomatoid and poorly differentiated subtypes. Some patients had known asbestos exposure, such as 15 years of changing brake linings. Others had none known. The review focused on microvilli, the finger-like projections on the tumor cell surface usually treated as a hallmark of the disease. Their length-to-width ratio ranged from about 40 in one well-differentiated case down to 8 in another. In one tumor, the number of microvilli differed from area to area. No microvilli were seen in the sarcomatous part of one biphasic tumor or in one poorly differentiated tumor. The authors concluded that one, several or even all of the usual electron microscope criteria for mesothelioma may be absent. In their view, a lack of long microvilli does not exclude the diagnosis when clinical, X-ray and surgical findings suggest mesothelioma.

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: Review of electron microscope (ultrastructural) features, based on the authors' own series of serosal tumors and illustrated with selected case descriptions
• Who was studied: 70 serosal tumors: 56 diffuse epithelial mesotheliomas, 10 localized fibrous mesotheliomas, 3 adenomatoid tumors and 1 angiomatoid mesothelioma. Of these, 11 lesions were selected for illustration (pleural and peritoneal cases in adults aged 41 to 77). The article does not state the study dates or the source of the cases.
• Exposure: Exposure was not studied as such; the case histories record it. One patient changed brake linings with intermittent asbestos exposure for 15 years. One worked 30 years in an asbestos manufacturing plant. One had a father exposed in shipbuilding. One had lung tissue with an abnormally high content of crocidolite fibers. Several had no known asbestos exposure.
• Main results:
  • In epithelial (tubulopapillary) Case 1, microvilli were exceptionally long, with a length-to-diameter ratio of about 40
  • In epithelial (nonglandular) Case 4, microvilli were shorter (ratio 14) than in the tubulopapillary cases and fell within the range reported for some adenocarcinomas
  • In epithelial (nonglandular) Case 5, from a man with 30 years in an asbestos manufacturing plant, microvilli were sparse and relatively short (ratio 8)
  • In papillary peritoneal Case 3, one area had fewer, shorter-looking microvilli than another area of the same tumor. The ratio (17) was not significantly different from the other area (20).
  • In biphasic Case 2 (lung tissue with high crocidolite content), the tissue available for electron microscopy showed only the sarcomatous component, and no microvilli were observed in it
  • The illustrated sarcomatoid mesothelioma had focal stretches of surface microvilli
  • In poorly differentiated Case 1, tumor cells lacked microvilli, intercellular junctions and external lamina
  • In the poorly differentiated cases, the authors report that immunostaining was positive for high-molecular-weight cytokeratins and negative for carcinoembryonic antigen
• The authors' conclusion: The authors concluded that one, several or all of the fine structural criteria usually required for a mesothelioma diagnosis may be absent. They concluded that mesothelioma should still be considered when clinical, radiologic and surgical evidence suggests it.
• Limitations the authors state:
  • The authors note that sampling affects what electron microscopy shows, since different areas of one tumor can look different

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Biphasic Mesothelioma, Well-Differentiated.

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