Anaplastic sarcoma in the caudal thigh of a horse.

This research article talks about a case study of a 16-year-old showjumping gelding horse that developed anaplastic sarcoma in the caudal thigh. The tumor was initially identified as a non-painful, slowly progressive swelling in the thigh, which led to slightly impaired movement during the trot. Despite medical imaging tests, the tumor could not be conclusively identified, but chest radiography revealed the presence of metastasis in the lungs. The diagnosis of anaplastic sarcoma was confirmed after the horse’s death through a postmortem examination.

Clinical Presentation

• The study revolves around a 16-year-old showjumping gelding horse which was reported to have a non-painful, slowly progressive swelling in the caudal thigh. The swelling was associated with a slight lameness at a trot, indicating a slight impairment in movement.

Diagnostic Methods

• Various imaging techniques including radiography, real-time beta-mode ultrasonography, and gamma-scintigraphy were used for diagnosing possible chip fractures, sequestrum formation, or abscessation in the caudal thigh. These techniques, however, did not provide a conclusive result.
• Further diagnostic examination of the chest through radiography revealed multiple nodular cannon ball-like opacities throughout the lung fields. This indicated a likelihood of metastasis from a primary soft tissue tumor.

Diagnosis and Postmortem Examination

• Based on the abnormalities identified in the lung via chest radiography, a provisional diagnosis of a primary soft tissue tumor with metastasis to the thorax was made.
• A diagnosis of anaplastic sarcoma, a form of a malignant tumor, was made postmortem in the caudal thigh. This confirmed the horse’s disease condition and the identification of the primary source of metastasis.

Clinical Progression and Absence of Respiratory Symptoms

• Despite the presence of a sarcoma in the thigh and metastasis in the lungs, the horse did not exhibit any signs of respiratory distress throughout its lifetime. This absence of respiratory symptoms can be considered an unusual feature in this case as metastasis in the lungs often leads to respiratory impairment.