Microcystic variant of localized malignant mesothelioma accompanying an adenomatoid tumor-like lesion

Our plain-English summary of Microcystic variant of localized malignant mesothelioma accompanying an adenomatoid tumor-like lesion, by H. Umezu, K. Kuwata, Y. Ebe, et al (Pathology International, 2002).

The study

• Authors: H. Umezu, K. Kuwata, Y. Ebe, T. Yamamoto, M. Naito, Y. Yamato, T. Ishiyama, M. Tsuchida, M. Okuizumi, H. Ishikawa, N. Koizumi
• Journal: Pathology International
• Published: 2002;52(5-6):416-22
• Type of article: Case report
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The case of a 70-year-old man with a hitherto undescribed pleural mesothelioma is reported. The tumor was localized in the left lung apex and had invaded the parietal pleura. Histologically, the tumor was characterized by a proliferation of epithelioid cells and the formation of microcysts. The tumor cells were positive for calretinin and vimentin, and possessed abundant microvilli, indicating a mesothelial cell origin for the tumor. A high Ki-67 index and mitotic index, and the recurrence of the tumor after surgery, indicated malignancy. Based on the evidence, we propose that the tumor is a microcystic variant of a localized malignant mesothelioma.

In plain English

This article was a case report from Niigata University, Japan, about one 70-year-old man with a pleural mesothelioma that the authors described as not previously reported. A shadow in his left lung was seen on a chest X-ray taken during follow-up for a heart attack. The article states he had no symptoms from the tumor and no history of asbestos exposure. The tumor sat at the top of the left lung and had invaded both the lung and the chest wall. Under the microscope it was made of many small cysts. The tumor cells stained strongly for calretinin and vimentin and had many long microvilli, which the authors took as signs that the tumor came from mesothelial cells. The Ki-67 growth index was 32.6% in the main tumor and 7.6% in a separate 4 mm adenomatoid tumor-like spot nearby. Eight months after surgery, malignant cells were found in fluid around the left lung. The authors concluded that the tumor was a malignant mesothelioma and proposed calling it a microcystic variant of localized malignant 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: case report (single patient), with pathology, immunohistochemistry and electron microscopy
• Who was studied: one 70-year-old man in Japan (Niigata University), found to have a left lung shadow during follow-up of myocardial infarction
• Exposure: The article states the patient had no history of asbestos exposure; no fiber type is given.
• Main results:
  • The main tumor was made of numerous small cysts lined by flattened or cuboidal cells.
  • The main tumor stained strongly for calretinin and vimentin and weakly for keratin and cytokeratin.
  • On electron microscopy, the tumor cells had numerous long microvilli on the cell surface.
  • In the main tumor, three or four mitotic figures were found in 10 high-power fields.
  • The Ki-67 index was 32.6% in the main tumor and 7.6% in the separate adenomatoid tumor-like lesion.
  • A separate 4 mm adenomatoid tumor-like focus was found in the visceral pleura, near but apart from the main tumor.
  • The tumor had invaded both the chest wall and the lung.
  • Eight months after the operation, the patient had left pleural effusion, and the fluid contained malignant cells. Hyaluronic acid in the fluid was 31 000 ng/mL and fell to 59 ng/mL after drug injection into the pleural cavity.
  • The patient was alive 2 years after the operation, with tumor shown on X-ray in the left pleural cavity.
• The authors' conclusion: The authors concluded that the tumor was a malignant mesothelioma and proposed it as a microcystic variant of localized malignant mesothelioma.

Topics

Medical terms in this study, explained in our Lexicon: Localized Malignant Mesothelioma, Adenomatoid Tumor, Pleural Mesothelioma, Parietal Pleura, Epithelioid, Calretinin, Mesothelial Cells, Ki-67.

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