Thoracic and Abdominal Mesothelioma in an Older Horse in Lazio Region

Our plain-English summary of Thoracic and Abdominal Mesothelioma in an Older Horse in Lazio Region, by G. Passantino, E. Sassi, I. Filippi, et al (Animals, 2022).

The study

• Authors: G. Passantino, E. Sassi, I. Filippi, V. Serata, A. Tinelli, N. Zizzo
• Journal: Animals
• Published: 2022;12(19)
• Type of article: Case report
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A Quarter Horse, a gelding aged 22, was subjected to a clinical examination for colic syndrome. During admission to the clinic, blood counts and ultrasound examination were performed. Ultrasound revealed abdominal masses and abundant accumulation of pleural (50 L) and abdominal fluid (100 L). Cytology was performed on the aspirated fluid. The patient was euthanized. The autopsy examination revealed abundant effusion and nodular masses on the peritoneum, omentum, lungs, heart, and mediastinum. A diagnosis of epithelioid mesothelioma was made via histopathology and confirmed with immunohistochemistry; it showed positive antibodies against cytokeratin (CK) and vimentin. Mesothelioma is a rare cancer in older horses. It is important to employ the correct differential diagnostics using the available methods, providing valid ante-mortem support to the clinical veterinarian and monitoring the territory using this species as a valid biological indicator.

In plain English

This article was a case report of one horse, a 22-year-old Quarter Horse gelding admitted to an equine clinic in Campagnano di Roma, in Italy's Lazio region, for colic pain. Ultrasound showed free fluid in the abdomen with rounded masses on the peritoneum. Draining the abdomen produced about 100 L and then about 60 L of fluid. The horse was euthanized after 5 days of poor response to treatment. At autopsy there were about 100 L of abdominal fluid and about 50 L of chest fluid, with nodules on the peritoneum, omentum, lungs, heart and mediastinum. Microscopic examination gave a diagnosis of epithelioid mesothelioma. Tumor cells stained positive for vimentin and cytokeratins, which the authors took as confirming mesothelial origin. Tumor cells were also found in abdominal and tracheobronchial lymph nodes. The authors thought the tumor most likely began in the peritoneum but could not rule out several origins. No asbestos exposure was measured. The authors noted the horse lived in an area with very high human mesothelioma incidence and proposed monitoring local horses as sentinels. They also stated that the cause of this tumor in horses is unknown.

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 animal)
• Who was studied: One 22-year-old male gelding Quarter Horse, stabled in a paddock and used in equestrian tourism, admitted to the equine clinic "Equine Practice s.r.l." in Campagnano di Roma (Rome), Lazio region, Italy. No date of the case is given.
• Exposure: No asbestos or other exposure was measured. The authors noted only that the horse lived in an area with a very high incidence rate of human mesothelioma, according to the National Mesothelioma Registry for Lazio.
• Main results:
  • During hospitalization, the first abdominal drainage produced about 100 L of serum-blood fluid and the second about 60 L.
  • The horse was euthanized after 5 days of hospitalization because of poor response to therapy and worsening condition.
  • At autopsy, the peritoneum and omentum carried numerous nodular masses up to 4 cm, and about 50 L of fluid was found in the chest cavity.
  • The histological diagnosis was epithelioid mesothelioma with a tubulo-papillary structure.
  • Tumor cells were positive for vimentin, CK AE1/AE3 and CK 8/18 in more than 75% of cells. CK 5/6 was positive in less than 25% of cells.
  • The abdominal and tracheobronchial lymph nodes were infiltrated by tumor cells.
• The authors' conclusion: The authors attributed the tumor to an environmental origin and proposed monitoring other horses in the same area, with horses serving as a biological indicator of the disease. They also wrote that the cause of this tumor in horses is still unknown and that the case shows how hard diagnosis is before and after death.
• Limitations the authors state:
  • The authors thought the tumor most likely started in the peritoneum but could not rule out a multicenter origin.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Ultrasound, Cytology, Autopsy, Peritoneum, Omentum, Mediastinum, Epithelioid.

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