Ultrastructural diagnosis of epithelial malignant mesothelioma

Our plain-English summary of Ultrastructural diagnosis of epithelial malignant mesothelioma, by T.R. Burns, S.D. Greenberg, M.L. Mace, et al (Cancer, 1985).

The study

• Authors: T.R. Burns, S.D. Greenberg, M.L. Mace, E.H. Johnson
• Journal: Cancer
• Published: 1985;56(8):2036-40
• Cited by: 42 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000462).

Abstract

Examination of microvilli (MV) by electron microscopy (EM) may help distinguish epithelial malignant mesotheliomas (EMM) from metastatic adenocarcinomas (AC). The goal of this study was to assess the diagnostic utility of microvillous length to width (l/w) measurements of EMM and AC, and to determine if ultrathin sections can be used to accurately assess lengths of villi not completely contained within a single section. Therefore, in addition to the usual ultrathin (600-800 A) sections used for standard transmission EM, thicker (up to 1 mu) sections were also prepared for study by scanning transmission EM. Seven cases of EMM and 3 of AC were analyzed. In each case, length and width were measured for all MV with identifiable bases (18-60 MV/case), using an electronic planimeter, and the mean l/w ratio calculated. The dimensionless l/w ratio is independent of magnification and does not require calibration, facilitating intercase comparison. In the 3 AC, the mean l/w was 5.39, versus 11.44 in the 7 EMM cases. Four EMM were analyzed using both standard ultrathin and thicker sections, disclosing a thin section l/w of 13.34 and a thick section of 12.26, supporting the confidence of measurements made from standard ultrathin sections. Examination of data also showed that equally good separation of EMM from AC could be obtained using the mean ratio of only the 10 longest MV (16.11 versus 8.93). By these techniques, EMM often may be distinguishable from AC, with a l/w ratio twice as large in EMM and a mean l/w greater than 11 supportive of a diagnosis of EMM.

In plain English

This small laboratory study used electron microscopy to test whether measuring microvilli, tiny finger-like projections on tumor cells, could help tell epithelial malignant mesothelioma apart from adenocarcinoma. Cases came from the files of the Baylor College of Medicine electron microscopy laboratory: 7 mesotheliomas and, for comparison, 3 primary lung adenocarcinomas, because no samples of adenocarcinoma spread to the pleura were available. In each case 18 to 60 microvilli were measured and a length-to-width ratio was calculated. The average ratio was 11.44 for the mesotheliomas and 5.39 for the adenocarcinomas (P less than 0.01). Using only the 10 longest microvilli gave 16.11 versus 8.93 (P less than 0.025). In 4 mesotheliomas, standard thin sections and thicker sections gave similar ratios (13.34 and 12.26), a difference the authors reported as not significant. The authors concluded that mesothelioma can often be distinguished this way and that an average ratio of 11 or greater is very suggestive of it. They cautioned that occasional overlap may appear as more cases are studied. Asbestos exposure was not analyzed.

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: Small diagnostic pathology study measuring microvilli on electron microscopy (morphometry) in selected tumor cases
• Who was studied: Tissue from 7 cases of epithelial malignant mesothelioma and 3 cases of primary adenocarcinoma of the lung, selected from the files of the Baylor College of Medicine electron microscopy laboratory, Houston, Texas. Several had been referred to one author for consultation. Dates were not given. Table 1 indicates that the mesotheliomas included pleural cases and at least one peritoneal case.
• Exposure: Not an asbestos exposure study. The measurement studied was the length-to-width ratio of microvilli. Table 1 lists occupational histories for some patients, including paper plant or paper company work, a history of asbestos exposure, and 'ship 8 years'. It also lists one case with ferruginous bodies in lung tissue, mainly amosite. The table text is too garbled to match these details to individual cases.
• Main results:
  • Mean length-to-width ratio of microvilli was 5.39 in the 3 adenocarcinomas versus 11.44 in the 7 mesotheliomas. The authors reported this difference as statistically highly significant (P less than 0.01).
  • Using only the 10 longest microvilli, the mean ratio was 16.11 for mesothelioma versus 8.93 for adenocarcinoma (P less than 0.025).
  • In 4 mesotheliomas examined with both methods, the mean ratio was 13.34 on standard ultrathin sections and 12.26 on thicker sections. The authors reported this difference as not significant.
  • The number of microvilli found varied considerably between cases. Between 18 and 60 were measured per case.
• The authors' conclusion: The authors concluded that epithelial malignant mesothelioma often may be distinguished from adenocarcinoma by this technique. In their data the ratio was about twice as large in mesothelioma, and they described an average ratio of 11 or greater as very suggestive of mesothelioma.
• Limitations the authors state:
  • The authors noted that occasional overlap of measurements between the two tumor types may occur as more cases are studied.
  • No electron microscopy samples of adenocarcinoma that had spread to the pleura were available. Primary lung adenocarcinomas were used for comparison instead.
  • Other features of mesothelioma, such as desmosomes and tonofilaments, were noted but not measured.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Adenocarcinoma.

Related studies

• Desmosomes of epithelial malignant mesothelioma — T.R. Burns, E.H. Johnson, et al. (1988)
• Diffuse epithelial mesothelioma: a review of the ultrastructural spectrum — I. Dardick, M. Jabi, et al. (1987)
• Adenomatoid tumour of the epididymis: histochemical and ultrastructural study of 2 cases — M. Nistal, F. Contreras, et al. (1978)
• An ultrastructural comparison of mesotheliomas with adenocarcinomas of the lung and breast — M.J. Warhol, J.M. Corson (1985)
• Ultrastructural features of diffuse malignant mesotheliomas — T.D. Oury, S.P. Hammar, et al. (1998)
• An ultrastructural comparison of mesotheliomas and adenocarcinomas of the ovary and endometrium — M.J. Warhol, N.J. Hunter, et al. (1982)

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