Pseudomesotheliomatous carcinoma of the lung. A variant of peripheral lung cancer

Our plain-English summary of Pseudomesotheliomatous carcinoma of the lung. A variant of peripheral lung cancer, by T.R. Harwood, D.R. Gracey, H. Yokoo (American Journal of Clinical Pathology, 1976).

The study

• Authors: T.R. Harwood, D.R. Gracey, H. Yokoo
• Journal: American Journal of Clinical Pathology
• Published: 1976;65(2):159-67
• Type of article: Case report
• Cited by: 117 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Six cases of primary lung cancer that closely mimic malignant pleural mesothelioma clinically and anatomically are compared with four proven cases of malignant pleural mesothelioma. Findings on roentgenograms of the chest, clinical history, and gross examination of the lung specimens are not helpful in distinguishing between these two neoplasms. Microscopic examination of the hematoxylin and eosin-stained tissues is often inconclusive. Tissues were stained with hematoxylin and eosin, PAS with and without diastase treatment (DPAS), mucicarmine, alcian blue, toluidine blue, and colloidal iron with and without digestion by testicular hyaluronidase. Among these histochemical methods, DPAS was found to be particularly useful in distinguishing the primary lung cancers from the mesotheliomas. All primary lung cancers except one showed DPAS-positive material (mucin) in both the cytoplasm of the cancer cells and within the lumina of neoplastic glands. In contrast, none of the mesotheliomas showed the presence of DPAS-positive material. Histologically, all lung cancers were glandular. Five were classified as bronchiolar carcinoma, the remaining one as poorly differentiated adenocarcinoma. In two of the bronchiolar carcinomas, a small subpleural primary focus was demonstrated. This finding suggests a possible origin of these cancers as a small subpleural tumor that became widely disseminated via the subpleural lymphatics. This form of primary lung cancer possesses sufficient gross and microscopic characteristics that recognition should be given to it as a variant of primary lung cancer, with emphasis on differentiating it from pleural mesothelioma.

In plain English

This was a case series from the V.A. Research Hospital and Northwestern University Medical School, Chicago. The authors described six men, aged 49 to 76, who died of primary lung cancer that closely resembled malignant pleural mesothelioma. At autopsy, tumor 0.3 to 2.0 cm thick infiltrated the fused pleural layers and completely encased the lung in five cases; in one, only the lower lobe was primarily involved. Chest x-rays, symptoms and the appearance of the lungs did not tell these cancers apart from mesothelioma, and in one case mesothelioma had been diagnosed. The authors compared tissue from four cases of malignant pleural mesothelioma. A mucin stain called DPAS (PAS after diastase) showed mucin both inside the cells and in the gland spaces in five of the six lung cancers, and in none of the mesotheliomas. Five cancers were bronchiolar carcinoma and one was poorly differentiated adenocarcinoma. One patient had worked in a shipyard in World War II with indirect asbestos exposure. Asbestos bodies were not found in any of the cases. The authors concluded this tumor should be recognized as a distinct form of peripheral lung cancer.

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 series of six autopsied cases, with tissue staining compared against four cases of malignant pleural mesothelioma
• Who was studied: Six men (aged 49 to 76, average 57 years) with primary lung cancer resembling pleural mesothelioma, first admitted 1967 to 1971 to the V.A. Research Hospital, Chicago. Four cases of malignant pleural mesothelioma were used for comparison.
• Exposure: Not a study of asbestos exposure. One patient (Case 1) had worked in a shipyard in World War II and had been indirectly exposed to asbestos. No asbestos bodies were found in any case. All patients smoked cigarettes except possibly Case 1, whose smoking history was not recorded.
• Main results:
  • DPAS staining: all lung cancers except one showed DPAS-positive material (mucin) both inside the cancer cells and in the gland spaces. None of the four mesotheliomas did.
  • Of the six lung cancers, five were classified as bronchiolar carcinoma and one as poorly differentiated adenocarcinoma. All were glandular.
  • Asbestos bodies were not found in any of the six lung cancer cases.
  • Except for one case in which only the lower lobe was primarily involved, the lungs were completely encased by tumor infiltrating the fused, thickened pleurae.
  • The tumor encasing the lung ranged from 0.3 to 2.0 cm thick. The left lung was involved three times, the right twice, and both lungs once.
  • A primary tumor was found in two cases, as small nodules under the pleura (0.7 and 1.5 cm in diameter). No primary site was identified in the other four.
  • Total duration of illness after symptoms began was less than 8 months. Dyspnea, chest pain and weight loss were the most frequent presenting symptoms.
  • Clinically, the diagnosis was uncertain without tissue confirmation in two cases, and in another case malignant mesothelioma was considered.
• The authors' conclusion: The authors concluded that, because of its characteristic gross and microscopic features, this cancer is justified in being recognized as a unique form of peripheral lung cancer. They stated that mucin inside the cells and gland spaces is perhaps the most useful feature for telling it apart from malignant pleural mesothelioma.
• Limitations the authors state:
  • The authors stated that the origin of the tumor is not clear. Their proposed sequence (chronic pleural scarring, then a scar-related carcinoma, then rapid spread across the pleura) is a hypothesis.
  • The authors stated that definitive diagnosis before death is virtually impossible on clinical grounds, because tumors elsewhere must be excluded by postmortem examination.

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: Pseudomesotheliomatous Adenocarcinoma, Lung Cancer, Pleural Mesothelioma, Neoplasm, Mesothelioma, Carcinoma, Adenocarcinoma.

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• Pseudomesotheliomatous carcinoma of the lung with asbestos exposure — J. Simonsen (1986)
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