Malignant epithelioid pleural mesothelioma versus peripheral pulmonary adenocarcinoma: a histochemical, ultrastructural, and immunohistologic study of 103 cases

Our plain-English summary of Malignant epithelioid pleural mesothelioma versus peripheral pulmonary adenocarcinoma: a histochemical, ultrastructural, and immunohistologic study of 103 cases, by M.R. Wick, T. Loy, S.E. Mills, et al (Human Pathology, 1990).

The study

• Authors: M.R. Wick, T. Loy, S.E. Mills, J.F. Legier, J.C. Manivel
• Journal: Human Pathology
• Published: 1990;21(7):759-66
• Cited by: 130 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The distinction between malignant epithelioid pleural mesothelioma (MEPM) and peripheral adenocarcinoma of the lung with pleural invasion (PAL) continues to represent a diagnostic challenge in selected cases. In order to provide comparative data on histologic, histochemical, and immunohistochemical features of these neoplasms, we analyzed 51 ultrastructurally categorized MEPMs and 52 PALs with the periodic acid-Schiff-diastase (PAS-D), mucicarmine, and colloidal iron stains, and a panel of immunohistologic reagents. Antibodies to cytokeratin, vimentin, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), Leu M1, the B72.3 antigen, blood group isoantigens (BGI), placental alkaline phosphatase, amylase, S100 protein, and Clara cell antigen were used, as applied to paraffin sections with the avidin-biotin-peroxidase complex technique. Ultrastructural studies revealed long, branching microvilli in MEPM cells in all cases, with length-to-diameter ratios (LDR) of 10:1 or more. In contrast, PAL manifested short, nonbranching microvilli with LDR of 8:1 or less. Reactivity with PAS-D and mucicarmine stains was strictly confined to PAL, and hyaluronidase-sensitive colloidal iron-positivity was restricted to MEPM. However, only 63% and 41% of these respective neoplasms demonstrated such histochemical reactivity. Immunohistologic results correlated well with electron microscopic classification. All MEPMs and PALs were reactive for cytokeratin; in addition, the majority of tumors in each group expressed EMA, and a minority were reactive for vimentin. In adenocarcinomas of the lung, Leu M1 was observed in all cases, CEA was apparent in 96%, B72.3 labeled 84%, and BGI were present in 67%; all PALs expressed at least two of these determinants, but none was seen in any mesothelioma. The other markers included in this study also were observed in some PAL cases, but not in MEPM. These findings suggest that immunohistology parallels electron microscopy in efficacy in the diagnostic separation of MEPM and PAL. Using antibodies to Leu M1, CEA, and the B72.3 antigen, reactivity for at least two of these three markers appears to exclude a diagnosis of pleural mesothelioma. The other glycoproteinaceous, oncoplacentofetal, and cytoplasmic antigens we studied can be used to reinforce such a determination, since their distribution is confined to adenocarcinomas.

In plain English

This laboratory study compared ways to tell apart two cancers that can look alike: malignant epithelioid pleural mesothelioma and peripheral lung adenocarcinoma that has spread to the pleura. The authors examined 51 mesotheliomas and 52 adenocarcinomas from three hospitals in Minnesota and Virginia, using electron microscopy as the reference standard. The study did not examine asbestos exposure. Under electron microscopy, mesotheliomas had long, branching surface projections (microvilli); adenocarcinomas had short ones. Stains for epithelial mucin (PAS-D and mucicarmine) were positive only in adenocarcinomas, but missed 37% of them. Colloidal iron staining that the enzyme hyaluronidase removed was seen only in mesotheliomas, in 21 of 51 (41%); five adenocarcinomas stained too, but hyaluronidase did not remove it. With antibody stains, all 103 tumors were positive for cytokeratin. Leu M1 was found in all 52 adenocarcinomas, CEA in 50 of 52 and B72.3 in 43. None of these three markers was found in any mesothelioma. The authors concluded that antibody staining matched electron microscopy. They also concluded that positivity for at least two of Leu M1, CEA and B72.3 appears to exclude pleural mesothelioma.

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: Retrospective comparative pathology study of archived tumor specimens using histochemical stains, electron microscopy and immunohistochemistry, with electron microscopy as the diagnostic standard
• Who was studied: 51 malignant epithelioid pleural mesotheliomas and 52 peripheral pulmonary adenocarcinomas with pleural involvement, from the surgical pathology files of the University of Minnesota Medical Center, the University of Virginia Health Sciences Center and Riverside Hospital (Newport News, VA); collection dates not given
• Main results:
  • Mesotheliomas showed long, elaborately branched microvilli; in all adenocarcinomas the microvillus length-to-diameter ratio was under 8:1
  • Neutral (epithelial) mucin stains (PAS-D and mucicarmine) were positive only in adenocarcinomas, but missed 37% of adenocarcinoma cases
  • Colloidal iron staining removed by hyaluronidase was seen in 21 of the 51 mesotheliomas and was restricted to mesotheliomas; its sensitivity was 41%
  • Five adenocarcinomas also showed colloidal iron staining, but it was not diminished by hyaluronidase pretreatment
  • All 103 tumors (both mesotheliomas and adenocarcinomas) were reactive for cytokeratin
  • Leu M1 was found in all 52 adenocarcinomas and in none of the 51 mesotheliomas
  • CEA was detected in 50 of 52 adenocarcinomas and in no mesothelioma
  • B72.3 labeled only adenocarcinomas, and was reactive in 43 of the 52
  • Every adenocarcinoma expressed either Leu M1 plus CEA or Leu M1 plus B72.3
  • Vimentin was present in 21 mesotheliomas and 9 adenocarcinomas
• The authors' conclusion: The authors concluded that immunohistology matched electron microscopy in separating the two tumors. They concluded that reactivity for at least two of Leu M1, CEA and B72.3 appears to exclude a diagnosis of pleural mesothelioma. They also said their results cast doubt on the practical usefulness of vimentin for this distinction.

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: Epithelioid, Pleural Mesothelioma, Adenocarcinoma, Neoplasm, Iron Stain (Prussian Blue), Epithelial Membrane Antigen (EMA), Carcinoembryonic Antigen (CEA), B72.3 (TAG-72).

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