564
EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2020) 32 (11) 564 doi: 10.1111/eve.13130_1
Case Report
Surgical treatment of a mandibular ameloblastic carcinoma with metastases to the mandibular lymph nodes in a pony A. M. Derham†*, A. Kushnir†
, S. Hoey†, H. Jahns† , A. R. Hollis‡ and C. M. Kearney†
†University Veterinary Hospital, University College Dublin, UCD, Belfield, Dublin 4, Ireland; and ‡Centre for Equine Studies, Animal Health Trust, Kentford, Newmarket, Suffolk, UK *Corresponding author email:
ann.derham@
ucdconnect.ie
Keywords: horse; cancer; jaw; mandibulectomy; tumour
Summary A 4-year-old Connemara filly was presented with an oral mass on the right rostrolateral mandible that had rapidly increased in size over the previous 7 days and a right mandibular lymphadenopathy. Oral examination revealed a large (approx. 4.5 cm L 9 3cm H 9 2cm W) firm, raised, ulcerated mass of the right rostral mandible involving the bone and gingiva. The mass expanded caudally within the gingival stroma; however, rostrally, there was no clear demarcation between the mass and mandibular bone. Axial compression of the deciduous third incisor was present, and eruption of the second incisor was reduced compared to the contralateral side (Fig 1). Radiographs of the rostral mandible revealed an expansile,
infiltrative mass consistent with soft tissue and mineralised material, and displacement of tooth 403. A deep-incisional biopsy showed characteristic histopathological features of an ameloblastic carcinoma (Fig 2). The diagnosis of carcinoma was based on the lack of peripheral basilar epithelial cells, high-mitotic rate, moderate anisocaryosis and central necrosis of some islands. The presence of odontogenic epithelium in the tumour was confirmed by immunohistochemical (IHC) staining using pan-cytokeratin and vimentin antibodies. The neoplastic cells were positive for both markers. Subsequent FNA of the right abnormally firm and enlarged mandibular lymph node confirmed metastatic spread.
Fig 2: Ameloblastic carcinoma, horse; large polygonal epithelial cells are irregularly arranged in islands, some of which show central necrosis and haemorrhage, in a dense fibrous stroma. H&E, 1003 magnification.
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 to 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 under general anaesthesia, 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.
Key points
• First report of a mandibular ameloblastic carcinoma with metastasis to the mandibular lymph nodes in the veterinary literature.
• Use of CT sentinel mapping was helpful in confirming the absence of other local lymph node involvement, resulting in more complete surgical planning.
Fig 1: Pre-operative image of the mass involving the right rostrolateral mandible with retraction of the lower lip.
• Rostralmandibulectomy allowed for complete removal of the lesion from the mandible, without disturbing the mandibular symphysis,andresultedin excellent cosmesis.
© 2019 EVJ Ltd
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