Malignant mesothelioma eight years after a diagnosis of atypical mesothelial hyperplasia

Our plain-English summary of Malignant mesothelioma eight years after a diagnosis of atypical mesothelial hyperplasia, by J. Scurry, M.A. Duggan (Journal of Clinical Pathology, 1999).

The study

• Authors: J. Scurry, M.A. Duggan
• Journal: Journal of Clinical Pathology
• Published: 1999;52(7):535-7
• Type of article: Case report
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The separation of mesothelial hyperplasia from early malignant mesothelioma remains one of the most difficult problems in histopathology. Inconclusive cases are termed "atypical mesothelial hyperplasia" and treated expectantly. A 49 year old male pipeline engineer was diagnosed as having atypical mesothelial hyperplasia in appendiceal serosa by the US-Canadian Mesothelioma Panel. Eight years later, he developed overtly malignant peritoneal and pleural mesothelioma. In hindsight, histological similarities between the diffuse malignant mesothelioma and the atypical mesothelial proliferation suggested malignancy from the outset. The most important of these features were the degree of mesothelial proliferation, micronodularity, architectural complexity, superficial invasion, uniform mild cytological atypia, and the absence of a clinical cause for a benign mesothelial proliferation. Ancillary investigations including immunohistochemistry were of no benefit in determining whether the atypical mesothelial hyperplasia was benign or malignant. Careful histological examination remains the mainstay of the diagnosis of early mesothelioma.

In plain English

This was a case report about one man. In 1989, a 49 year old male pipeline engineer who had worked in fertiliser and gas processing plants on three continents since 1981 had his appendix removed for suspected appendicitis. Small nests of mildly atypical mesothelial cells were found on and beneath its surface, and the US–Canadian Mesothelioma Panel diagnosed atypical mesothelial hyperplasia. Panel members favoured a benign outcome, but the chairman cautioned about the degree of cell growth. In 1997 he was diagnosed with diffuse malignant mesothelioma, epithelioid type, involving the peritoneum and pleura. The tumour cells resembled the 1989 cells but were slightly more atypical. Staining for p53 and Ki67 was negative in both samples, and the tumour's DNA content was normal; the authors said such tests did not help. The article described only potential occupational asbestos exposure, naming no fiber type, and no asbestos fibre count was performed on the tumour tissue. The authors concluded that the 1989 change was, in hindsight, probably already malignant mesothelioma, and that careful microscopic examination remains the key to diagnosis.

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 report (single patient)
• Who was studied: One patient: a 49 year old male pipeline engineer, first seen in 1989 and followed to 1997. The country where he was treated is not stated. The authors were based in Melbourne, Australia and Calgary, Canada.
• Exposure: Potential occupational asbestos exposure from work in fertiliser and gas processing plants since 1981. The authors counted eight years of potential exposure by 1989 and 16 years by 1997. No fiber type was named, and no asbestos fibre count was performed on the tumour tissue.
• Main results:
  • In 1989 the appendix serosa showed scattered nests and small nodules of epithelioid cells, up to 1.0 mm across, on and beneath the surface. The cells were later confirmed as mesothelial and showed mildly atypical features.
  • The US–Canadian Mesothelioma Panel diagnosed the 1989 appendix changes as atypical mesothelial hyperplasia.
  • Panel members favoured a benign prognosis. The panel chairman cautioned that such a degree of proliferation had not previously been seen in a benign case.
  • In 1997 the final diagnosis was diffuse malignant mesothelioma, epithelioid type, involving the peritoneum and pleura.
  • The 1997 tumour cells were similar to the 1989 appendix cells but slightly more atypical.
  • p53 and Ki67 immunostaining was completely negative in both the 1989 and 1997 specimens.
  • Benign reactive mesothelium from another patient, used as a control, showed p53 reactivity in 5% of cells and Ki67 reactivity in 10% of cells.
  • Flow cytometry of the omental tumour showed normal DNA content: 100% of cells diploid, DNA index 1.00.
  • The authors reported that ancillary tests, including immunohistochemistry, did not help decide whether the atypical mesothelial hyperplasia was benign or malignant.
  • No asbestos fibre count was performed on the tumour tissue.
  • In hindsight, the authors listed the features of the 1989 biopsy that suggested early malignancy. These were its similarity to the later tumour, the degree of proliferation, stromal invasion, architectural complexity, uniformly mild cytological atypia, and the absence of any cause for benign hyperplasia.
  • Comparing the two biopsies, the authors judged that the 1989 biopsy was in hindsight probably already malignant mesothelioma.
• The authors' conclusion: The authors concluded that the 1989 atypical mesothelial hyperplasia was probably already early malignant mesothelioma. They also argued that its appearance after only eight years of potential asbestos exposure supports this. They concluded that careful histological examination remains the key to diagnosing early mesothelioma.

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, Atypical Mesothelial Proliferation, Reactive Mesothelial Hyperplasia, Histopathology, Pleural Mesothelioma, Immunohistochemistry.

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