Ultrastructurally "invasive" microvilli in an aggressively metastasizing biphasic malignant mesothelioma

Our plain-English summary of Ultrastructurally "invasive" microvilli in an aggressively metastasizing biphasic malignant mesothelioma, by Y. Zu, G.S. Sidhu, R. Wieczorek, et al (Ultrastructural Pathology, 2002).

The study

• Authors: Y. Zu, G.S. Sidhu, R. Wieczorek, N.D. Cassai
• Journal: Ultrastructural Pathology
• Published: 2002;26(6):403-9
• Type of article: Case report
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The presence of long, slender, often branching microvilli on cell surfaces is a characteristic feature of malignant and benign mesothelial cells. However, these typical microvilli are seen only in better-differentiated lumens within epithelial areas of malignant mesotheliomas. Presented here are the clinical and ultrastructural findings in a biphasic malignant mesothelioma that lacked lumens, but possessed very long microvilli. These invaginated deeply into the cytoplasm of neighboring tumor cells, as well as into the surrounding stromal matrix. The tumor cells had well-formed intercellular desmosomal junctions. The primary tumor was localized to the pleura and invaded the chest wall, but only minimally the lung. Lobectomy demonstrated the presence of metastatic tumor in 2 peribronchial lymph nodes. The disease progressed rapidly and, within 6 months, killed the patient. An autopsy revealed widespread metastases in multiple systemic organs. The authors speculate that the unique ultrastructural features of this case may be a clue to the unusually aggressive course of the neoplasm.

In plain English

This case report described one patient, a 69-year-old black man in New York with a biphasic malignant mesothelioma that formed a localized pleural mass over the right upper lobe, invading the chest wall but only minimally the lung. The authors took his construction work as presumptive asbestos exposure, although no asbestos bodies were found in lung sections under the light microscope. He had smoked cigarettes for over 50 years. When the lobe and part of the chest wall were removed, tumor was found in 2 peribronchial lymph nodes. He died 6 months later, and the autopsy found metastases in the heart, both lungs, liver, spleen, pancreas, kidneys and left adrenal gland. Under the electron microscope, the tumor cells had very long, slender microvilli (finger-like surface projections), the longest with a length-to-diameter ratio of 23:1. These commonly extended deep into neighboring tumor cells and, in some places, projected into the surrounding tissue. The authors speculated that these features may be a clue to the tumor's unusually aggressive course. Because no similar cases had been reported, they said they could not offer statistical evidence for this.

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), with light microscopy, immunohistochemistry, electron microscopy and autopsy findings
• Who was studied: one 69-year-old black man seen at a New York Harbor Healthcare hospital with a pleural mass over the upper lobe of the right lung; year of presentation not stated
• Exposure: work in the construction industry, which the authors interpreted as presumptive asbestos exposure. No fiber type or dose was given, and asbestos bodies were not found on light microscopy of lung sections. The patient also had a smoking history of over 50 years.
• Main results:
  • The primary tumor was localized to the pleura and invaded the chest wall but only minimally the lung. Tumor had spread to 2 peribronchial lymph nodes at the time of lobectomy.
  • The patient died 6 months after surgery. At autopsy, metastases were found in multiple organs.
  • Tumor cells stained strongly positive for calretinin and positive for WT-1 (markers the authors took as supporting mesothelioma). They were negative for BerEp4, CEA and CD15.
  • On electron microscopy, the longest microvillus had a length-to-diameter ratio of 23:1.
  • The microvilli of neighboring tumor cells commonly extended deep into each other's cytoplasm, which the authors said had not been reported before.
  • At some places, similar microvilli projected into the surrounding tissue and touched collagen fibrils.
  • No asbestos bodies were found on light microscopic examination of lung sections.
• The authors' conclusion: The authors concluded that the findings supported a diagnosis of mesothelioma. They speculated that the unusual microvilli may be a clue to the tumor's unusually aggressive course.
• Limitations the authors state:
  • The authors stated that their proposed explanation for how the microvilli enter neighboring cells is completely speculative.
  • The authors stated they could not offer statistical evidence linking the microvilli to the aggressive spread, because no similar cases have been reported.
  • The authors noted that the localized tumor mass was highly atypical for biphasic mesothelioma and pointed toward lung carcinoma, although they judged the overall findings to favor 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: Biphasic Mesothelioma, Malignant Mesothelioma, Mesothelial Cells, Pleura, Autopsy, Neoplasm.

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