A 4-year-old Connemara filly was presented with a rapidly growing oral mass on the right rostrolateral mandible and a right mandibular lymphadenopathy. Radiographs of the rostral mandible revealed a lytic, infiltrative mass consistent with soft tissue and mineralised material, and displacement of tooth 403. A biopsy showed characteristic histopathological features of an ameloblastic carcinoma. Subsequent FNA of the right abnormally firm and enlarged mandibular lymph node confirmed the metastatic spread. Computed tomography of the head was performed for surgical planning, including sentinel lymph node mapping to rule out other lymph node involvement. An aggressive lesion, consistent with soft tissue of the rostral right mandible was identified with intralesional contrast injection showing drainage of contrast within the right mandibular lymph nodes (Sentinel node). Based on the infiltrative and destructive nature reported in ameloblastic carcinoma in humans, a rostral mandibulectomy was performed, along with complete mandibular lymphadenectomy. The horse recovered uneventfully from surgery. In the early post-operative period marked lymphoedema of the ventral mandibular region was observed, which resolved 4-5 days post-operatively. Optimal cosmesis was maintained post-operatively, and no recurrence has been observed to date-12 months post-surgery.

Duplication cysts of the gastrointestinal tract in mammals are rare congenital anomalies that arise during embryonic development. Finding these cysts in a juvenile Grey seal is also a rare observation. We report here a coincidental finding of two gastrointestinal duplication cysts in a 4-week-old female Grey seal, which was found on a beach on the East coast of Ireland. Gross anatomical features of the esophagus and pylorus together with the histological features of the cyst are presented.