Diffuse Mesotheliomas: Observer Variation In Histological Diagnosis

Our plain-English summary of Diffuse Mesotheliomas: Observer Variation In Histological Diagnosis, by W.T.E. Mccaughey, P.D. Oldham (1973).

The study

• Authors: W.T.E. Mccaughey, P.D. Oldham
• Published: Biological Effects Of Asbestos (J.C. Wagner, Editor), Lyon: Iarc Scientific Publications, Volume 8, Pp. 58-61 (1973)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 002398. The article is still under copyright, so we describe it here rather than post it.

In plain English

This paper examined how much pathologists disagreed when diagnosing diffuse mesothelioma from tissue slides. First, the authors analysed records of a mesothelioma panel that had assessed suspected cases since 1964. At least two members saw each case, and a third if they disagreed. When pairs of frequent members were the first two assessors, a third was needed in about 12% to 18% of their cases, or almost a third for C and D. Second, pleural tumour sections, including several metastatic tumours, went to three observers with a questionnaire on microscopic features. Of 27 sections with completed questionnaires, all three rated 7 as probable or definite mesothelioma, and 6 as definitely not or possible but unlikely mesothelioma. All or most observers were uncertain in 9, and there was gross disagreement in 5. In all 5, one observer who was not a panel member gave a definite negative. Even where diagnoses agreed, answers on individual features differed widely, and some histological terms were used differently. The authors concluded that diagnosis by experienced observers was highly subjective and that more systematic studies were needed.

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: Observer-variation study of histological diagnosis: an analysis of a mesothelioma panel's record books, plus circulation of a small group of slides to observers with a structured questionnaire
• Who was studied: Records of a panel of nine members who had assessed suspected mesotheliomas since 1964. A set of pleural tumour sections, including several metastatic tumours, was read by three observers, with completed questionnaires for 27 sections; three further observers later read the sections. The authors were based in Dublin and at the MRC Pneumoconiosis Unit, Penarth, UK.
• Exposure: Not applicable: the study concerned pathologists' readings of tumour slides; no asbestos exposure was assessed
• Main results:
  • In the panel records, member A saw about three in four cases, B and C about one in two, D about one in four, and the other members seldom took part
  • When they were the first two assessors, pairs of panel members disagreed (the case was sent to a third assessor) in about 18% of cases for A, B and D with each other (A and B: 17 of 92). For C, the figures were about 12% with A (11 of 93), about 14% with B (6 of 43), and almost a third of cases with D
  • In the slide study, all three observers gave category 3 or 4 (probably or definite mesothelioma) for 7 of 27 sections
  • All three observers gave category 0 or 1 (definitely not, or possible but unlikely, mesothelioma) for 6 of 27 sections
  • Even in cases where all observers gave a positive category, answers to the detailed questions on microscopic features showed substantial disagreement in almost every instance
  • All 5 cases of gross disagreement involved the same observer giving a definite negative while the other two gave category 3 or 4. This observer had not been a panel member, and the second set of observers sided with the other two
  • In the 9 uncertain cases, agreement on individual questions was noticeably better than in the cases where the diagnosis was certain
  • At a review meeting, the observers found marked differences in how they interpreted histological detail, and found that some histological terms were applied in different ways
• The authors' conclusion: The authors concluded that histological diagnosis of mesothelial tumours by experienced observers is highly subjective and that more systematic studies are needed. They also said the implications for the panel's work were not discouraging.
• Limitations the authors state:
  • The authors described the panel records as rather limited information
  • From the records, it was not possible to tell which of the first two observers the third member agreed with
  • The authors said considerably more systematic studies were needed to understand how observers weigh the uncertainties in diagnosis

Topics

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

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