Surgical treatment of a mandibular ameloblastic carcinoma with metastases to the mandibular lymph nodes in a pony

Abstract

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.

Ameloblastic carcinoma in horses: case report and literature review

“…Detailed studies investigating cytokeratin and vimentin expression at different stages of odontogenesis demonstrate the transient co-expression of cytokeratin and vimentin intermediate filaments in the external enamel epithelium, internal enamel epithelium (pre-ameloblasts), and stellate reticulum cells of the enamel organ. 9,13 Furthermore, studies have demonstrated this dual expression in ameloblastoma and ameloblastic carcinoma in humans, dogs, and horses, 3,4,[8][9][10]14,22 which likely reflects a recapitulation of the expression pattern of primitive odontogenic tissue (i.e., dental lamina or enamel organ).…”

“…5 However, ameloblastic carcinoma is exceedingly rare, is reported uncommonly in humans, 5,21 and only a few cases have been reported in horses, dogs, and a rat. 3,4,8,10,11,14,17,22 In addition to ameloblastoma, a primary differential diagnosis for ameloblastic carcinoma is oral squamous cell carcinoma. These 2 neoplasms can have considerable overlap in gross and histologic features, particularly in poorly differentiated squamous cell carcinomas that may have a spindloid phenotype and scant keratinization.…”

“…5 However, ameloblastic carcinoma is exceedingly rare, is reported uncommonly in humans, 5,21 and only a few cases have been reported in horses, dogs, and a rat. 3,4,8,10,11,14,17,22…”

“…To our knowledge, ameloblastic carcinoma has been reported previously in only 4 horses in the peer-reviewed literature, 3,4,14,22 with detailed, pathology-focused histologic description and images provided in only 1 case 3 (Table 1). The neoplasm involved the maxilla in 2 cases and the mandible in the other 2 cases.…”

“…19 In these cases, identification of 1 or more odontogenic epithelial features, as well as dual expression of cytokeratin and vimentin, are key for distinguishing between these 2 neoplasms. 3,8,9,13,19 Only 4 cases of equine ameloblastic carcinoma are reported in the peer-reviewed literature, 3,4,14,22 and only 1 of these reports thoroughly details the gross and histologic features of an equine ameloblastic carcinoma. 3 Here we review features of published cases of equine ameloblastic carcinoma and describe the clinical progression, radiographic findings, and gross and histologic morphology of an ameloblastic carcinoma in a horse.…”