Diffuse malignant pleural mesothelioma and asbestos exposure

Our plain-English summary of Diffuse malignant pleural mesothelioma and asbestos exposure, by F. Whitwell, R.M. Rawcliffe (Thorax, 1971).

The study

• Authors: F. Whitwell, R.M. Rawcliffe
• Journal: Thorax
• Published: 1971;26(1):6-22
• Cited by: 164 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001382).

Abstract

Pleural mesothelioma has been diagnosed in 52 patients in three hospitals on Merseyside between 1955 and 1970, 60% being diagnosed from operation specimens and the rest from postmortem tissues. Necropsies eventually held on nearly half the operation cases confirmed the diagnosis, giving a necropsy rate of 70% for the series. The morbid anatomy conformed to earlier descriptions except that widespread metastases were much commoner than has usually been described. Histological findings agreed with previous accounts of the tumour, except that, in our hands, special acid mucopolysaccharide staining was less reliable than Southgate's mucicarmine, which was of value in differential diagnosis. Association with asbestos was confirmed from industrial histories in 80% of cases, the commonest industries involved being shipbuilding and repairing in men and sackware repairing in women. Lungs of industrial mesothelioma cases showed basal asbestosis in 17% and excessive asbestos bodies in almost all the rest. Quantitative comparison of asbestos bodies in lung smears from mesothelioma cases compared with lung smears from other Merseyside adults showed much higher counts in the mesothelioma cases. The interval from first exposure to asbestos until appearance of mesothelioma ranged between 13 and 63 years, with a mean of 42 years. We think the incidence of mesothelioma will continue to rise with the increased use of asbestos until about 40 years after adequate protective measures have been taken.

In plain English

This case series, continuing an earlier one by Owen, covered 52 people with diffuse malignant pleural mesothelioma diagnosed between 1955 and 1970 at three Merseyside hospitals in England. Industrial histories confirmed asbestos exposure in 80% of cases. This included 35 of the 40 men, mostly from shipbuilding and ship repair. It also included 8 of the 12 women, six of whom had handled used sacks that sometimes held asbestos. The article does not name fiber types. For 33 patients with known dates, the time from first exposure to first mesothelioma symptoms ranged from 13 to 63 years (mean 42). Of 30 exposed patients examined at autopsy, all had asbestos bodies in the lungs and 5 (17%) had basal asbestosis. In the last 14 such autopsies, none with asbestosis, 13 showed 12 or more asbestos bodies per lung smear. Of 200 consecutive autopsies on adults over 30, excluding known pneumoconiosis, 24% showed any; 85% of positive smears had fewer than 12. Distant spread was common in later autopsies. The authors concluded that mesothelioma would keep rising until about 40 years after adequate protection.

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 series of pleural mesothelioma patients from three hospitals. The authors describe it as a prospective continuation of an earlier, largely retrospective Merseyside series (Owen, 1964).
• Who was studied: 52 patients with pleural mesothelioma (40 men, 12 women) diagnosed between 1955 and 1970 at Broadgreen and Aintree Hospitals, Liverpool, and St. Catherine's Hospital, Birkenhead. Of these, 14 came from Owen's earlier 17 cases and 38 were added between 1963 and 1970. The comparison group was lung smears from 200 consecutive autopsies at Broadgreen Hospital in 1966-7, on patients of both sexes over age 30, excluding known pneumoconiosis.
• Exposure: Industrial asbestos dust exposure. Men were exposed mainly in shipbuilding and ship-repairing trades. Women were exposed in bag and sack repair works, handling used hessian sacks that had sometimes contained asbestos. Other exposures were dock-side work, lagging, an asbestos factory and a brake-lining factory. Exposure duration was known for 36 patients and ranged from three years to over 50 years. Fiber types are not named.
• Main results:
  • Across the series, association with asbestos was confirmed from industrial histories in 80% of cases.
  • Among the men, 35 of 40 had significant asbestos dust exposure: 28 in shipbuilding and repairing, 3 in dock-side occupations, and 4 in non-maritime jobs.
  • Among the 12 women, 8 had a definite history of industrial asbestos exposure. Six of these had worked in bag and sack repair works, and two had worked in asbestos factories before moving to Merseyside.
  • The interval from first asbestos exposure to first mesothelioma symptoms was measured in 33 patients whose dates were known. It ranged from 13 to 63 years, with a mean of 42 years.
  • Lungs of 30 mesothelioma patients with a history of asbestos exposure were examined at autopsy. All contained asbestos bodies, and basal asbestosis was present in five cases (17%).
  • In the comparison group of 200 routine autopsies, asbestos bodies were present in 24% (33% of men, 13% of women). Of the 48 positive smears, 41 (85%) showed fewer than 12 bodies per smear.
  • Smears were counted in the last 14 autopsied asbestos-exposed mesothelioma patients, none of whom had asbestosis. One showed fewer than 11 asbestos bodies per smear, five showed 12 to 24, and eight showed between 25 and over 1,000.
  • Blood-borne metastases were found in only one of the first 10 autopsies (Owen's cases) but in 14 of the next 22 autopsies.
  • Among 36 patients with known symptom onset, 53% survived one year, 33% two years, 17% three years, and 8% (three cases) over five years.
  • Survival was compared from the time of histological diagnosis. All of an earlier series of 419 inoperable lung cancer patients had died by 18 months, while 26% of the 30 mesothelioma patients diagnosed from operation specimens were still alive.
  • Smoking habits were recorded for 28 patients. The interval from first exposure to tumour was no shorter in smokers than in non-smokers.
  • Owen found 12 asbestos-induced mesotheliomas between 1955 and 1963, and the authors found 31 more in the same hospitals between 1964 and 1970. The authors took this to suggest a real and large increase.
• The authors' conclusion: The authors concluded that mesothelioma incidence will continue to rise with increased asbestos use until about 40 years after adequate protective measures are taken. They also concluded that, when asbestosis is absent, lung smear asbestos body counts can help distinguish industrial from urban asbestos exposure.
• Limitations the authors state:
  • The lung juice smear method is less searching than many other described methods.
  • Asbestos bodies could be found in only four of the surgical specimens, which usually contained little lung tissue.
  • The earlier retrospective part of the series was probably incomplete, because tumours that had spread were not accepted as mesotheliomas.
  • Only three of the nine non-industrial cases had autopsies. Three others showed atypical staining, which raised slight doubt about their diagnosis.
  • Too few cases lacked occupational asbestos contact to draw significant conclusions about sex distribution among them.
  • Asbestos bodies are common in urban lungs, so their presence alone does not imply excessive or industrial exposure.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Asbestos Exposure, Autopsy, Differential Diagnosis, Mesothelioma, Asbestos Bodies.

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• Diffuse pleural mesothelioma with distant bone metastasis. A case report — R.N. Laurini (1974)
• Pleuropneumonectomy in the management of diffuse malignant mesothelioma of the pleura. Experience with 29 patients — E.G. Butchart, T. Ashcroft, et al. (1976)
• Aetiology of pleural plaques — V. Rous, J. Studený (1970)
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