Cranial mediastinal liposarcoma in a horse.

This study details the clinical event of a 23-year-old horse developing a large, abnormal fatty tumor in the chest cavity which was identified as a liposarcoma, a rare occurrence in horses.

Introduction

• In this clinical case study, the authors present a liposarcoma – which is a cancer that arises from fat cells – in the cranial mediastinum part of a 23-year-old horse. This is an unusual finding as liposarcomas in the cranial mediastinum, which is the area in the chest between the lungs, are not common occurrences for horses.

Initial Clinical Symptom

• The horse was initially presented with symptoms such as tachypnea (rapid breathing), dyspnea (shortness of breath), and edema around the ventral thoracic subcutis area, which is the lower part of the chest.

Necropsy Findings and Diagnosis

• Upon necropsy, a large, irregularly shaped mass was found in the cranial mediastinum of the horse. This mass was tan to red in color and had a friable texture, meaning it was easily broken apart. The dimensions of this mass were substantial, measuring 23 cm x 20 cm x 18 cm.
• Histological analysis – the study of microscopic structures – of the mass confirmed it to be a liposarcoma.
• The liposarcoma was characterized by short, interlacing bundles of spindle-shaped to irregularly rounded cells each demonstrating clear cytoplasmic vacuoles of variable sizes within them. These cytoplasmic vacuoles stained positive with oil red O, a lipid stain, thus confirming them to be fat cells. The examination was conducted on frozen sections of the formalin-fixed tissue.

Conclusion

• The study describes an atypical occurrence of a liposarcoma in the cranial mediastinum of a horse. This case sheds light on the need for more scrutiny in diagnosing and dealing with respiratory distress and subcutis edema in horses, as it could be indicative of serious underlying conditions like mediastinal liposarcomas.