Abstract
Background: To describe the clinical presentation and treatment of an ectopic periorbital lymph node in two young horses.
Case Description: Two Warm-Blood horses were presented at the equine clinic of the University of Liège with a periorbital non-painful mass. Differential diagnosis included neoplasm (lymphoma), (sterile) abscess, cyst, ectopic lacrimal gland tissue, hematoma, adipose tissue or ectopic lymphoid tissue. Information collected included physical and ophthalmic examination findings, results of ocular and periocular ultrasound, surgical procedure, histopathology and follow-up. Masses of 2x2cm and 3x2cm subcutaneous, ovoid, smooth, and firm mass were observed in the zygomatic region of the head. On ultrasound, the mass appeared as a hypoechoic subcutaneous structure. Cytology showed a mixed lymphocytic cell population. No abnormal mitotic activity was observed. Histopathology revealed a chronic markedly reactive lymph node.
Conclusion: To the authors’ knowledge, this is the first description of periorbital ectopic lymph nodes in veterinary medicine. Ectopic lymph node should therefore be included in the differential diagnosis of periocular masses in animals. Surgery was easily performed and was curative.

Key words: ectopic lymph node, eye, eyelid, horse, mass