Ultrastructural histochemistry of mesotheliomas and adenocarcinomas in malignant effusions

Our plain-English summary of Ultrastructural histochemistry of mesotheliomas and adenocarcinomas in malignant effusions, by P. Barsotti, A.O. Muda, V. Ascoli, et al (Diagnostic Cytopathology, 1989).

The study

• Authors: P. Barsotti, A.O. Muda, V. Ascoli, P. Casareale, F. Nardi
• Journal: Diagnostic Cytopathology
• Published: 1989;5(2):154-61
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The results of electron microscopic examination of cytologic specimens from six cases of mesothelioma and 10 cases of metastatic carcinoma of different origins are presented. The formation of cell clusters in malignant effusions from the two neoplasms has been thoroughly investigated: in mesotheliomas, cells had longer, more slender microvilli than in carcinomas and more abundant bundles of intermediate filaments; the central cavity often seen in the clusters frequently contained collagen and showed basement membrane production. The application of periodic acid-silver methenamine (PASM) and phosphotungstic acid (PTA) demonstrated a peculiar ultrastructural difference in cell coat staining in the two tumor types: in mesotheliomas, PTA and PASM were consistently negative along the outer surface of the cell aggregates, while carcinomas displayed a positive reaction either on the outer surface or on both inner and outer surfaces of the clusters. The diagnostic significance of the above-mentioned difference between the two neoplasms will require further investigation in a larger number of cases.

In plain English

This laboratory study, from a university pathology department in Rome, Italy, examined fluid samples from the chest or abdominal cavity of 16 patients. Six had diffuse mesothelioma and 10 had carcinoma (a cancer that had spread from another organ). The authors looked at clumps of tumor cells in the fluid under the light microscope and the electron microscope, using special stains called PASM and PTA. On ordinary smears the two cancers were hard to tell apart. In mesothelioma, cells had long, slender surface projections. Most of the material at the center of the cell clumps was collagen, and in many instances a basement membrane (a thin supporting layer) lined the central cavity. Carcinoma cells had shorter, more irregular projections and no collagen. PTA never stained the mesothelioma cell surface, while carcinomas stained on the outer surface of the clumps or, rarely, on both surfaces. The authors concluded that whether this staining difference helps diagnosis will require study of more cases. The article does not discuss asbestos exposure.

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: Descriptive laboratory case series: light and electron microscopic histochemistry of cytologic specimens from malignant effusions
• Who was studied: 16 patients whose pleural and/or peritoneal fluid was sampled: 6 with diffuse mesothelioma (4 pleural, 2 peritoneal, per Table II) and 10 with metastatic carcinoma of different origins. Diagnoses were confirmed by biopsy and/or surgery. The study came from a university department in Rome, Italy. Dates of collection are not given.
• Main results:
  • On Papanicolaou-stained smears, telling the two tumor types apart was difficult because they shared several common features.
  • In mesotheliomas, PASM staining was strongly positive in the cores of most cell clusters. In adenocarcinomas, most cores did not react.
  • Mesothelioma cells formed long, slender microvilli (surface projections) toward the outside of the clusters.
  • In mesotheliomas, most of the material seen at the center of the clusters proved to be collagen bundles.
  • In mesotheliomas, a well-developed basement membrane was seen in many instances lining the central cavity of the clusters.
  • In mesotheliomas, PTA never reacted with the cell membrane.
  • Carcinoma cells had shorter, more irregular microvilli than mesothelioma cells, and collagen deposition was not present.
  • In carcinomas, PTA and PASM gave a positive reaction on the outer surface of the clusters or, in rare instances, on both inner and outer surfaces.
  • In carcinomas, mucin granules were frequently seen beneath the positively stained cell coat in a number of cases.
  • The authors noted that finding basement membrane formation in mesothelioma clusters seemed to contradict the common opinion that it appears only in adenocarcinoma cell clumps.
• The authors' conclusion: The authors concluded that the consistent PTA and PASM negativity along the outer surface of mesothelioma clusters is a distinctive histochemical difference between the two tumors. They stated that whether this feature is of diagnostic significance by itself will require further study in more cases.
• Limitations the authors state:
  • The authors stated that the diagnostic significance of the staining difference needs to be studied in a larger number of cases.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Adenocarcinoma, Carcinoma, Neoplasm, Collagen.

Related studies

• The distinction of adenocarcinoma from malignant mesothelioma in cell blocks of effusions: the role of routine mucin histochemistry and immunohistochemical assessment of carcinoembryonic antigen, keratin proteins, epithelial membrane antigen, and milk fat globule-derived antigen — E.S. Cibas, J.M. Corson, et al. (1987)
• Utility of HBME-1 immunostaining in serous effusions — V. Ascoli, C. Carnovale-Scalzo, et al. (1997)
• Cytological differential diagnosis among adenocarcinoma, epithelial mesothelioma, and reactive mesothelial cells in serous effusions by immunocytochemistry — X.Y. Su, G.D. Li, et al. (2011)
• Diagnostic problems in serous effusions — C.W. Bedrossian (1998)
• Calretinin. A selective marker of normal and neoplastic mesothelial cells in serous effusions — M.C. Barberis, M. Faleri, et al. (1997)
• Quality control of immunocytochemical staining of effusions using a standardized method of cell processing — V. Kuenen-Boumeester, P. van Loenen, et al. (1996)

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