Disseminated metastatic intramedullary melanoma in an aged grey horse.

The research article discusses a case where a 12-year-old grey Warmblood stallion developed fever, anemia, and later ataxia and had to be euthanized. The postmortem revealed malignant melanomas scattered throughout the skeleton, which is reportedly the first case of such extensive metastatic intramedullary melanoma in a domestic animal.

Presentation and Diagnosis

• The 12-year-old stallion initially presented with an unidentified fever and anemia. Five days later, it developed ataxia (loss of full control of body movements) and became recumbent (unable to rise).
• Due to the severity of the condition, it was humanely euthanized. The researchers performed an autopsy on the horse.

Autopsy Findings

• During autopsy, malignant melanomas (a form of skin cancer that arises from the pigment-producing cells known as melanocytes) were found in various parts of the body.
• Specifically, these melanomas were spotted in the perineal subcutis (a layer of skin found near the rectum), spleen, and the thoracic vertebral canal (in the T10-11 area, located at the mid-back of the horse).
• Interestingly, populations of these malignant melanoma cells had spread throughout the medullary cavities (the inner part of the bone that usually contains bone marrow) of both the axial (head, neck, and trunk) and appendicular (limbs) parts of the skeleton.
• The presence of these melanoma cells in the bone marrow resulted in the irregular areas of black to gray discoloration observed in the tissues.

Significance and Uniqueness of the Findings

• This research is significant as, according to the authors, this is the first reported instance of such wide-spread intramedullary melanoma in a domestic species.
• The extensive disseminated metastatic behavior of the melanoma identified in this horse is particularly noteworthy – instead of forming localized tumors, these cancer cells infiltrated the entire skeleton of the horse.