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  Discussion on Lympnosarcoma
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Posted on Friday, Feb 4, 2000 - 4:29 am:

I have a yearlying draft horse filly with very strange blood results. Among other things her lymphocytes are extremely elevated while the neutrophils are normal or just slightly raised. Tests were done because the filly is not growing and her condition is falling off. Her coat is dry and harsh and she is potbellied. The most likely diagnosis is lymphosarcoma. A specialist pathology lab is now looking at her latest bloods, results not available at this time. I thought lymphosarcoma was a disease of old(er) horses. There seems to be very little literature on this condition in horses.Interestingly, the filly's dam was ill while carrying the foal, although her condition is now good. Her blood is also somewhat abnormal, indicating a problem with the immune system or bone marrow. Any information on equine lymphosarcoma, or other diagnostic alternatives, would be appreciated. Thanks, Ann

Posted on Monday, Feb 7, 2000 - 1:37 pm:

Hello Annp:
I believe that your post has been overlooked. I will try to help. My information comes from the text Current Therapy in Equine Medicine 2nd edition.
Lymphosarcoma, although the overall prevalence is not high, it is one of the most common internal neoplasms affecting the horse. Unlike many neoplasms, lymphosarcoma is not restricted to old horses. The text states that 50% of the reported cases occured in horses from 4 to 9 years of age and, it has been seen in several horses less than a year old. The clinical signs vary depending on the organ involvement. The disease may be classified as one of four forms; however, there is considerable overlap between these groups: ailmentary, mediastinal, cutaneous, and generalized. As stated before there is some overlap of clinial signs between the above forms. The ailmentary, mediastinal, and generalized forms can all show chronic weight loss, anorexia (loss of appetite), depression, and intermittent fever. The other signs that each may show varies with the organs involved. Therefore, a diagnosis of lymphosarcoma cannot be made solely on the basis of clinical signs.
The list of diagnoses to rule out is extensive because of the many different clinical signs that may accompany lymphosarcoma. Common causes of weight loss such as malnutrition, poor dentition, and chronic lameness may be ruled out on the basis of a good history and physical exam. Gastrointestinal parasitism must always be considered in horses with weight loss or chronic colic or both. In horses with fever in addition to weight loss and colic, abdominal abscessation and other forms of neoplasia (gastric squamous cell carcinoma) must be ruled out.
Confirmation of the diagnosis of lymphosarcoma requires lab testing. To make a definitive antemortem diagnosis of lymphosarcoma, neoplastic lymphcytes must be detected in peripheral blood, bone marrow, peritoneal or pleural fluid, or in an aspirate or biopsy sample of a lymph node or tumor mass. Many horses with lymphosarcoma are anemic, presumably because of the anemia of chronic disease. However, immune-mediated hemolytic anemia occasionally occurs in horses with lymphosarcoma. According to the text, the most reliable method to establish the diagnosis of lymphosarcoma is histopathologic examination of a biopsy specimen from a lymph node or tumor mass. Your vet will know how to do a biopsy. I will tell you that the biopsy sample can be obtained with a biopsy needle; however, tissue obtained by surgical excision retains better morphology and improves the chances of a definitive diagnosis. I hope this information has been helpful. Sincerely, Dr. Woodworth

Posted on Monday, Feb 28, 2000 - 1:56 am:

Many thanks to Dr Woodworth.
Since posting the message, the filly has been on a course of antibiotics. She is picking up in condition. The lab has found no cancer cells and her blood tests are closer to normal. Her dam's blood was also tested and there are similarities. The dam's blood suggests a mild problem with her immune system or perhaps bone marrow. My vet indicated that there is a remote possibility of the development of leukaemia later on. My vet and I believe it is more than coincidence that both dam and foal have haemolytic abnormalities but there are no definitive tests currently available, just "wait and see". I will advise of further developments, if any.

Posted on Monday, Feb 28, 2000 - 8:04 am:

Thank you for keeping us appraised Ann,
DrO
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