Solid epithelioid peritoneal mesothelioma with pulmonary metastasis in feline

Our plain-English summary of Solid epithelioid peritoneal mesothelioma with pulmonary metastasis in feline, by H.C.T. de Carvalho, L.F. Gundim, F.M. Pastor, et al (Brazilian Journal of Veterinary Medicine, 2024).

The study

• Authors: H.C.T. de Carvalho, L.F. Gundim, F.M. Pastor, G.H. Guimarães, A.F. Coleto, M.P.J. Szabó, A.A. Medeiros-Ronchi
• Journal: Brazilian Journal of Veterinary Medicine
• Published: 2024;46:e004523
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Mesothelioma is a rare malignant neoplasm that affects the mesothelial cells lining the thoracic and abdominal cavities, such as the pleura, peritoneum, and pericardium. It is most prevalent in dogs and cattle, but the causes of this disease in animals are uncertain. In felines, it mainly affects the pleura, with an unfavorable prognosis. This paper explores a rare case of metastatic peritoneal mesothelioma in a 2-year-old female mixed breed cat, emphasizing its uniqueness due to the feline's age. The patient, previously treated at a private clinic, presented moderate abdominal distension as the only clinical sign. Abdominal ultrasound and peritoneal fluid cytology led to the provisional diagnosis of mesothelioma/carcinomatosis. One day after exploratory laparotomy, the animal died and was subsequently sent for necropsy. During macroscopic analysis, nodules were observed in the peritoneum, diaphragm, omentum, stomach serosa, and large intestine, and the diagnosis of solid epithelioid peritoneal mesothelioma with lung metastasis was confirmed after microscopic analysis. The diagnosis of mesothelioma is challenging, and the importance of immunohistochemical panels with specific markers such as cytokeratin AE1/AE3 and calretinin is highlighted. Considering that mesothelioma is a pathology with a poor prognosis, it is essential to include this disease in the list of differential diagnoses within veterinary oncology.

In plain English

This article is a case report about one cat in Brazil. The 2-year-old female mixed-breed cat had moderate abdominal swelling as its only recorded sign. Ultrasound showed abdominal fluid, and testing it gave a provisional diagnosis of mesothelioma or carcinomatosis. The cat died the day after exploratory surgery and was sent to a university veterinary hospital for necropsy. Examiners found many firm, whitish nodules 0.2 to 2.0 cm across in the peritoneum, diaphragm and omentum and on the outer surfaces of the stomach and large intestine, and tiny nodules throughout the lungs. Microscopy and staining led to a diagnosis of solid epithelioid peritoneal mesothelioma that had spread to the lungs. Cytokeratin AE1/AE3 and calretinin staining was strong in more than 75% of the omentum sample but weak in less than 25% of the lung sample; neither sample stained for vimentin. The authors called the cat's young age unusual among reported feline cases. The article reported no asbestos or fiber exposure for this cat. The authors concluded that the case underscored this disease's rarity and diagnostic difficulty in veterinary medicine.

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: Veterinary case report (one animal), based on necropsy, histopathology and immunohistochemistry
• Who was studied: One 2-year-old female mixed-breed cat, referred for necropsy to the Veterinary Hospital of the Universidade Federal de Uberlândia (HOVET-UFU), Uberlândia, MG, Brazil. The article gives no date for the case.
• Exposure: No exposure was assessed or reported for this cat. Asbestos appears only in the introduction, as background about humans and about an earlier study of urban dogs.
• Main results:
  • The cat's only clinical sign in the record sent with it was moderate abdominal distension
  • At necropsy, 22.0 mL of thick, dark red fluid was collected from the abdominal cavity
  • The peritoneum, diaphragm, omentum, stomach serosa (outer surface) and large intestine had multiple firm, whitish nodules from 0.2 to 2.0 cm in diameter
  • The lungs had multiple millimeter-sized, firm, whitish nodules spread throughout. The lymph nodes in the chest and abdomen showed no visible changes.
  • Under the microscope, the nodules showed round to oval cells in a solid pattern, with on average seven to eight mitotic figures per high-power field
  • Cytokeratin AE1/AE3 staining was strong in more than 75% of the omental nodule sample and weak in less than 25% of the lung nodule sample
  • Neither the omental nor the lung sample stained for vimentin
  • Calretinin staining was strong in more than 75% of the omental sample and weak in less than 25% of the lung sample
  • The final diagnosis was solid epithelioid peritoneal mesothelioma with pulmonary metastasis
  • The authors judged that the lung nodules, with no visible lymph node changes, suggested spread through the bloodstream
  • The authors noted that this cat, at 2 years, was younger than the previously reported feline peritoneal cases they cited (ages 4 to 17 years)
• The authors' conclusion: The authors concluded that this case of metastatic peritoneal mesothelioma in a 2-year-old cat underscored the rarity of the condition and the difficulty of diagnosing it in veterinary medicine. They also concluded that combined macroscopic, microscopic and immunohistochemical examination confirmed the diagnosis.
• Limitations the authors state:
  • The cat's complete medical record from the private clinic was not provided

Topics

Medical terms in this study, explained in our Lexicon: Epithelioid, Peritoneal Mesothelioma, Metastasis, Mesothelioma, Neoplasm, Mesothelial Cells, Pleura, Peritoneum.

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