A case of unsuspected peritoneal mesothelioma occurring with colonic adenocarcinoma masquerading as peritoneal metastases

Our plain-English summary of A case of unsuspected peritoneal mesothelioma occurring with colonic adenocarcinoma masquerading as peritoneal metastases, by W. Xie, L.K. Green, R.A. Patel, et al (Case Reports in Pathology, 2014).

The study

• Authors: W. Xie, L.K. Green, R.A. Patel, S. Lai
• Journal: Case Reports in Pathology
• Published: 2014;2014:838506
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

We report a case of synchronous primary colonic adenocarcinoma and malignant mesothelioma. A 61-year-old male presented with a six-month history of fatigue and weight loss. An abdominal computed tomography (CT) scan showed a 5.8 cm partially obstructing mass in the cecum with ascites and peritoneal thickening. A biopsy of the large mass showed an adenocarcinoma. Because the patient was clinically thought to be a T4 colon carcinoma with peritoneal metastatic lesions (M1), prior to initiating chemotherapy, a debulking right hemicolectomy was performed. Resection of the colon and ileum revealed a T3N0 colonic mucinous adenocarcinoma and concurrent diffuse malignant peritoneal mesothelioma. Presenting synchronous colonic and peritoneal mesothelial primary malignancies are exceedingly rare but must be considered to prevent incorrect clinical staging.

In plain English

This was a case report from pathologists in Houston describing a 61-year-old man with worsening diarrhea, fatigue, weight loss and abdominal pain. He was a Navy veteran with an unknown service record and a retired quality control factory worker who once worked in construction. The authors wrote that he did not have a clear documented source of exposure to asbestos. A biopsy of a colon mass showed adenocarcinoma. Scans were read as that cancer having spread to the abdominal lining, so he was staged as having unresectable colon cancer with peritoneal metastasis. After surgery to remove part of his colon, the colon cancer was found in none of 31 lymph nodes examined and was staged T3, N0. The nodules on the abdominal lining turned out to be a separate cancer: multifocal peritoneal malignant mesothelioma, epithelioid type, identified by its appearance under the microscope and by staining tests. He declined further treatment and was reported alive at 56 months. The authors concluded that this combination is exceedingly rare but must be considered to prevent incorrect clinical staging.

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
• Who was studied: One 61-year-old man, a Navy veteran and retired quality control factory worker who once worked in construction, treated in Houston, Texas, USA (Baylor College of Medicine and Michael E. DeBakey VA Medical Center).
• Exposure: No clear documented asbestos exposure. The authors noted that his Navy service, factory work and construction work could each have involved potential asbestos exposure. No fiber type was identified. He had a 40 pack-year smoking history.
• Main results:
  • Before surgery, CT and PET findings led to clinical staging of the patient as T4 unresectable colon adenocarcinoma with peritoneal metastasis (M1).
  • In the surgical specimen, none of the 31 lymph nodes examined contained metastatic adenocarcinoma, and the colon cancer was staged T3, N0.
  • The nodules on the peritoneal surfaces, presumed during surgery to be spread of the colon cancer, were diagnosed as a second, separate tumor: multifocal peritoneal malignant mesothelioma, epithelioid type.
  • On staining tests, the colon adenocarcinoma was positive for CK20, monoclonal CEA and villin and negative for calretinin, CK5/6 and CK7. The peritoneal tumor showed the opposite pattern.
  • The patient declined further treatment and continued to need periodic drainage of abdominal fluid, but was reported alive 56 months after diagnosis.
• The authors' conclusion: The authors concluded that synchronous colonic and primary peritoneal mesothelial cancers are exceedingly rare but must be considered to prevent incorrect clinical staging, and that tissue examination with immunohistochemistry is critical for definitive diagnosis.
• Limitations the authors state:
  • Because the combination is so rare, the authors stated it is difficult to say why the two tumors occurred together (by chance, environmental factors or shared genetic abnormalities).

Topics

Medical terms in this study, explained in our Lexicon: Peritoneal Mesothelioma, Adenocarcinoma, Mesothelioma, Ascites, Biopsy, Carcinoma, Chemotherapy, Staging.

Related studies

• An unusual case of isolated peritoneal metastases from lung adenocarcinoma — A. Bazine, M. Fetohi, et al. (2014)
• Perineal and colonic metastases in two cases of malignant mesothelioma — B. Grewal, G. Reid, et al. (2012)
• Benign multicystic mesothelioma with concurrent colonic adenocarcinoma: a report of two cases — A. Husain, M. Ozdemirli (2012)
• Localized malignant pleural mesothelioma arising in the interlobar fissure: a unique surgical case masquerading clinicopathologically as primary lung adenocarcinoma — X. Guo, J. Watanabe, et al. (2019)
• A case of lung adenocarcinoma complicated by pulmonary talcosis occurring in a patient employed in the confectionery industry — K. Kobayashi, N. Watanabe, et al. (2019)
• Colonic invasion induced by malignant peritoneal mesothelioma — S.B. Cao, S. Jin, et al. (2014)

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