Fibrosarcoma over the tarsal groove of a 14-month-old Quarter horse.

The research discusses a case where a 14-month-old male Quarter horse suffered from a type of cancer called Fibrosarcoma, found in the rear limb of the horse. The cancer was treated successfully with resection (a type of surgical procedure).

Initial Presentation

• The paper explores a case where a 14-month-old male Quarter horse was evaluated due to a right rear lameness, graded 3 out of 5— grade 0 indicating sound and grade 5 being non-weight bearing.
• Examination revealed a firm, 8 x 16 cm mass at the rear region (the caudal medial aspect of the distal tibia and proximal tarsal region) of the right hind limb.

Diagnosis Process

• A percutaneous needle aspirate, a procedure where a thin needle is introduced into the body to obtain cells for microscopic examination, was performed. The extract contained mesenchymal cells (cells that can transform into a variety of cell types) that were moderately large with single, elongated nuclei.
• Based on these results, the initial differential diagnoses hinted towards three conditions— fibrous hyperplasia (excessive tissue growth), fibroma (a benign tumor), or well-differentiated fibrosarcoma (an intermediate- to high-grade malignant smooth muscle tumor).

Treatment and Outcome

• Excisional biopsy, a surgical procedure where the entire lesion or tumor is removed, was offered as reliable choice for both diagnosis and treatment. This was preferred by the horse’s owner.
• Post-surgery, a histological examination, a study of the microscopic structure of tissues, confirmed the mass to be fibrosarcoma.
• One and a half years post-resection (removal), neither signs of lameness nor the regrowth of the tumor were observed, suggesting a successful treatment.