Oncofetal protein IMP3, a new diagnostic biomarker to distinguish malignant mesothelioma from reactive mesothelial proliferation

Our plain-English summary of Oncofetal protein IMP3, a new diagnostic biomarker to distinguish malignant mesothelioma from reactive mesothelial proliferation, by M. Shi, A.E. Fraire, P. Chu, et al (The American Journal of Surgical Pathology, 2011).

The study

• Authors: M. Shi, A.E. Fraire, P. Chu, K. Cornejo, B.A. Woda, K. Dresser, K.L. Rock, Z. Jiang
• Journal: The American Journal of Surgical Pathology
• Published: 2011;35(6):878-82
• Cited by: 55 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The distinction of malignant mesothelioma from reactive mesothelial proliferation remains to be a major challenge for surgical pathologists. In this study, we investigated whether insulin-like growth factor II messenger ribonucleic acid-binding protein 3 (IMP3), an oncofetal protein, can be used as a biomarker to distinguish between malignant and reactive mesothelial cells. A total of 109 cases (mesothelioma, n=45; reactive mesothelial proliferation, n=64) were examined by immunohistochemistry for IMP3 expression. IMP3 showed strong cytoplasmic staining in 33 of 45 (73%) mesothelioma cases. In contrast, the expression of IMP3 was undetectable in all (64 cases) benign reactive mesothelial proliferations. Among the IMP3-positive mesotheliomas, 27 (82%) exhibited diffuse IMP3 expression. The vast majority of IMP3-positive subtypes of mesotheliomas showed IMP3 expression in >50% of malignant cells, as this diffuse staining pattern occurred in 17 (81%) cases of epithelial, 4 (100%) cases of sarcomatoid, and 6 (75%) cases of mixed types of mesothelioma. In addition, 2 cases, which were initially diagnosed as atypical mesothelial proliferations and later confirmed to be mesotheliomas, showed diffuse IMP3 expression. Our findings suggest that IMP3 is a new positive biomarker for malignant mesothelioma. IMP3 immunohistochemical staining can be used as an adjunct tool in the distinction of malignant mesothelioma from reactive mesothelial proliferations.

In plain English

This laboratory study tested whether staining tissue for a protein called IMP3 could help pathologists tell malignant mesothelioma apart from reactive mesothelial proliferation, a benign, self-limited condition that can look similar. The authors examined 109 archived tissue samples from two US medical centers, collected between January 1997 and April 2010: 45 malignant mesotheliomas (38 pleural, 7 peritoneal) and 64 reactive proliferations. The study did not look at asbestos exposure. IMP3 stained positive in 33 of 45 mesotheliomas (73%). In 27 of these 33, the staining was diffuse, covering more than half of the tumor cells. Positive staining was seen in all three subtypes: 21 of 27 epithelioid, 8 of 10 mixed and 4 of 8 sarcomatoid. None of the reactive proliferations stained. Two cases first called atypical proliferations stained strongly, and both patients died from mesothelioma. The authors concluded that, used together with standard microscope criteria, IMP3 staining can be a useful aid. They cautioned that the test missed some mesotheliomas, so a negative stain does not necessarily mean a lesion is benign.

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: Laboratory (immunohistochemistry) study of archived tissue samples; diagnostic marker study
• Who was studied: 109 cases from UMass Memorial Medical Center (104) and City of Hope National Medical Center (5), collected January 1997 to April 2010. The cases were 45 malignant mesotheliomas (27 epithelioid, 10 mixed, 8 sarcomatoid; 38 pleural, 7 peritoneal) and 64 reactive mesothelial proliferations.
• Exposure: Not studied. The article reports no asbestos or other exposure information; it tested staining for the protein IMP3 in tissue samples.
• Main results:
  • IMP3 staining was positive in 33 of 45 (73%) malignant mesotheliomas.
  • No reactive mesothelial proliferation showed IMP3 staining. The results text says 62 cases; Table 2 and the abstract say 0 of 64.
  • Of the 33 IMP3-positive mesotheliomas, 27 (82%) showed diffuse staining in more than 50% of malignant cells.
  • Positive staining by subtype was 21 of 27 (78%) epithelioid, 8 of 10 (80%) mixed and 4 of 8 (50%) sarcomatoid mesotheliomas.
  • By location, IMP3 was positive in 27 (71%) of the 38 pleural mesotheliomas and in 6 (86%) of the 7 peritoneal mesotheliomas.
  • Two cases initially diagnosed as atypical mesothelial proliferation both showed strong, diffuse IMP3 staining, and both patients died from mesothelioma soon after diagnosis.
• The authors' conclusion: The authors concluded that IMP3 staining, used together with standard microscopic (histologic) criteria, can be a useful additional tool for distinguishing malignant mesothelioma from reactive mesothelial proliferations.
• Limitations the authors state:
  • IMP3 did not detect every mesothelioma (positive in 33 of 45), so a negative stain in a suspicious case does not necessarily mean the lesion is benign.
  • Routine microscopic (histologic) evaluation is still needed to establish a malignant diagnosis.

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: Biomarker, Malignant Mesothelioma, Reactive Mesothelial Cells, Mesothelioma, Immunohistochemistry, Sarcomatoid, Atypical Mesothelial Proliferation.

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