Adenomatoid tumor of the pleura

Our plain-English summary of Adenomatoid tumor of the pleura, by H. Minato, T. Nojima, N. Kurose, et al (Pathology International, 2009).

The study

• Authors: H. Minato, T. Nojima, N. Kurose, E. Kinoshita
• Journal: Pathology International
• Published: 2009;59(8):567-71
• Type of article: Case report
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A case of adenomatoid tumor of the pleura is reported, and its differential diagnosis from benign and malignant pleural lesions is discussed. A small pleural nodule was incidentally found during a thoracic operation in a 54-year-old woman with esophageal cancer. The patient had no history of exposure to asbestos, and was well with no sign of recurrence 14 months after the operation. A 7 mm, circumscribed tumor had characteristic features of adenomatoid tumor. The tumor was composed of an aggregation of irregularly shaped tubulocystic spaces with fibrous stoma. The spaces were lined by flattened and occasional cuboidal epithelioid cells with cytoplasmic vacuolization, and several spaces contained pale blue mucinous fluid. On immunohistochemistry the tumor cells were positive for AE1/AE3, CAM5.2, vimentin, cytokeratin 5/6, D2-40, calretinin, thrombomodulin, and WT-1, but negative for CEA, Leu M1 (CD15), thyroid transcription factor-1, epithelial membrane antigen, desmin, glucose transporter-1 (GLUT-1), CD31, and CD34. The MIB-1 (Ki-67) labeling index was 1-2%, indicating low proliferative activity. Adenomatoid tumor of the pleura is rare, and the pathogenesis has not been elucidated. Recognition of these benign mesothelial lesions in the pleura is important to avoid misdiagnosis. The immunohistochemistry in the present case supports its mesothelial origin.

In plain English

This case report described one patient, a 54-year-old Japanese woman with advanced esophageal cancer and no known history of exposure to asbestos. During her chest operation, surgeons found a small nodule on the parietal pleura (the lining of the chest wall) that imaging had not shown. Under the microscope it was a 7 mm, relatively well-defined tumor made of small irregular tube-like and cyst-like spaces. It showed no invasive growth and no dividing cells. Staining showed the tumor cells carried markers of mesothelial cells, including calretinin, cytokeratin 5/6, D2-40 and WT-1, and lacked carcinoma markers such as CEA and TTF-1. A growth marker (Ki-67) was low, at 1 to 2%. Fourteen months after surgery she had no chest symptoms, and imaging showed no pleural tumor. The authors diagnosed a benign adenomatoid tumor. They concluded that recognizing such benign mesothelial lesions is essential to avoid misdiagnosis, and that more cases with longer follow-up are needed to clarify how these tumors behave.

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 discussion of differential diagnosis
• Who was studied: One 54-year-old Japanese woman with advanced esophageal cancer, treated at Kanazawa Medical University, Japan; she also had a 16-year history of dermatomyositis and 2 years of primary biliary cirrhosis
• Exposure: No known history of exposure to asbestos
• Main results:
  • A small pleural nodule, not detected on imaging, was found incidentally in the right parietal pleura during the chest operation; no pleural thickening or other nodules were found
  • The tumor measured 7 mm, was circumscribed, and had the characteristic features of adenomatoid tumor
  • No mitosis was seen, and no invasive growth was observed
  • The tumor cells were positive for mesothelial markers (calretinin, CK5/6, D2-40, thrombomodulin, WT-1) and negative for the carcinoma markers CEA, LeuM1 and TTF-1. The authors said this strongly supported a mesothelial origin
  • The Ki-67 (MIB-1) labeling index of the tumor was 1–2%, indicating low proliferative activity
  • Fourteen months after surgery the patient had no chest discomfort or respiratory symptoms, and radiology showed no pleural tumor or effusion
• The authors' conclusion: The authors concluded that adenomatoid tumors of the pleura are rare and their cause is unclear. Recognizing these benign mesothelial lesions is essential to avoid misdiagnosis, and clinical, radiological, microscopic and immunohistochemical findings can distinguish them from other benign and malignant pleural lesions.
• Limitations the authors state:
  • More similar cases with longer follow-up are needed to clarify how pleural adenomatoid tumors truly behave
  • A low proliferative index alone cannot separate benign from malignant lesions
  • No lung tissue was obtained, because the tumor was in the parietal pleura

Topics

Medical terms in this study, explained in our Lexicon: Adenomatoid Tumor, Pleura, Differential Diagnosis, Esophageal Cancer, Epithelioid, Immunohistochemistry, CAM5.2, Cytokeratin 5/6.

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