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What is Lymphosarcoma?

The lymph system uses lymph nodes and tissues in various sites in the body to help battle disease by destroying infections and producing white blood cells. Often referred to as glands, lymph tissues are found throughout the body and within organs, such as the intestines and skin. When cancer invades one of the lymph areas, it can spread throughout the body within the vast network of the lymph system.

Lymphosarcoma is a type of cancer that attacks the lymph tissues of the body. Tumors often form in lymph nodes, and can spread to various other parts of the body, causing a myriad of symptoms and associated problems. While most common in horses aged 5 to 10 years old, it can affect any age, breed, or sex of horse, and carries a low rate of recovery due to the fact it is often diagnosed late in the progression of the disease.

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Symptoms of Lymphosarcoma in Horses

Signs of this condition can vary, and will reflect the area of the body or any organ involved. Tumors can develop in a number of sites, such as in the limbs, head, trunk, sinuses, nasal passage, tongue, jaw, eyes, mammary tissues, larynx, joints, and in various organs such as the spleen, heart, or uterus. Symptoms include:

  • Enlarged lymph nodes
  • Skin tumors that exude yellow fluid
  • Ulcerated skin tumors
  • Itchy skin
  • Jaundice 
  • Hair loss
  • Various internal tumors
  • Chronic weight loss
  • Abdominal swelling
  • Abdominal distension 
  • Abdominal pain 
  • Swelling in trunk or limbs
  • Depression 
  • Lethargy
  • Recurrent fever
  • Respiratory distress 
  • Coughing
  • Loss of condition 
  • Loss of appetite
  • Increased thirst
  • Increased pulse
  • Increased respiratory rate
  • Blood in the urine 
  • Urinary or fecal incontinence 
  • Chronic diarrhea
  • Jugular vein distension
  • Muffled heart sounds
  • Neurological signs
  • Loss of control of body movements 
  • Horner’s syndrome
  • Masses in eyes, eyelids and third eyelid
  • Intermittent eyelid swelling 
  • Chronic ocular discharge 
  • Chronic uveitis 
  • Increased levels of calcium
  • Malabsorption syndrome 
  • Lymphadenopathy, a disease of the lymph nodes
  • Low levels of proteins in blood
  • Seizures 

Types

There are different recognized types of lymphosarcomas, which are defined by location.

Generalized or Multi-Centric

This type is the most common kind of lymphosarcoma in horses, and involves multiple lymph node areas, such as near the jaw, base of neck, and in the throat. Various organs and body systems can be affected as it spreads through the lymph system. Common signs are large chest tumors, and masses near the lymph nodes themselves.

Cutaneous

This type of skin cancer involves tumors in the skin, and does not usually migrate into other areas of the body. Cutaneous tumors are the least deadly, and many horses can live a long time with mild symptoms of nodules that can ooze yellow fluid and become ulcerated.

Alimentary or Intestinal

This type involves the gastrointestinal tract, and commonly the tissues in the intestinal wall, causing malabsorption and protein-losing conditions. Common symptoms include weight loss, diarrhea, abdominal pain, and colic.

Mediastinal 

Also known as thoracic or thymic lymphoma, the most common area for tumors to infect is the thorax. This type affects the heart, breathing function, and can cause a distention of the jugular vein.

Solitary

These are tumors that have formed in extranodal sites, and can include organs like the spleen and heart, nasal passages and sinuses, mouth, and eyes. Many eye conditions such as conjunctiva, sclera and uveitis can be indicative of this kind of lymphoma.

Causes of Lymphosarcoma in Horses

Cancer is defined as an abnormal growth of cells that can develop into tumors. The true cause of why those cells grow uncontrollably remains unknown.

In lymphosarcoma, the abnormal growth affects the lymph tissue, often beginning in one location and spreading to other lymph areas through the lymph system, which includes lymph nodes and lymph tissues in various parts of the body. Once established, the tumors excrete chemicals that cause the many side effects seen in cancers, which often indicate an immunologic response to the foreign invader.

Diagnosis of Lymphosarcoma in Horses

Often diagnosed late in the progression of the disease, lymphosarcoma can be difficult to diagnose if tumors are not visible, due to symptoms that are similar to other conditions. Medical history, present symptoms, and a physical exam can lead to a diagnosis, but often testing is needed to confirm. Tumors and the spread of the disease can be seen in ultrasounds of the thorax and abdomen. If a tumor is present, a biopsy can confirm lymphosarcoma, but the procedure can cause further spread of the disease.

A chest auscultation can reveal muffled heart sounds, while thoracic percussion can detect fluid in the chest cavity. Bloodwork is done, as well as serum testing. Palpation of accessible organs can also reveal masses. Aspiration or biopsies of lymph nodes can also be performed.

If tumors are not obviously visible, other tests may be performed to narrow down the possible conditions. Biopsied tissue can be collected from duodenal or rectal tissues, and abdominal fluid can be tested for possible weight loss diseases.

Treatment of Lymphosarcoma in Horses

Treatments for lymphosarcoma are often difficult and expensive, and is often more supportive than curative. Many horses do not survive past a few weeks or months.

Corticosteroids are most often prescribed to suppress the immune system, and may prolong survival time, showing an improvement of symptoms over several weeks. Surgery can be performed to excise tumors but is more often restricted to solitary tumors.

Radiation treatments, mainly through brachytherapy and teletherapy, can be used, depending on the amount of spread and locations of the tumors. Chemotherapy can be curative if there is only a solitary mass. In most cases of lymphosarcoma, chemotherapy can cause a remission of the cancer but needs to be continued to prevent the likely return of the disease. During these treatments, physical exams are performed and blood counts are taken to monitor your horse’s health and recovery.

Other treatments include various herbal remedies, and the administration of synthetic progestin in mares, as it has been seen to reduce or eliminate cutaneous tumors.

Recovery of Lymphosarcoma in Horses

Recovery is dependent on the type of lymphosarcoma your horse has and how far the disease has spread. Cutaneous lymphosarcoma has the best rate of recovery. Solitary tumors that can be removed also carry a better chance of survival. Alimentary lymphosarcoma, however, has a poor rate of recovery. While some treatments can cause a remission of the disease, it does often return.