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Diagnosis and surgical treatment of a malignant trichoepithelioma of the ear canal in a pet rabbit (Oryctolagus cuniculus)

Casey BudgeonDepartments of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Christoph MansDepartments of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Tamara ChamberlinPathobiology, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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John SteinDepartments of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Randi DreesDepartments of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Cecilia RobatMedical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Marie PinkertonPathobiology, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Denise M. ImaiPathobiology, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Jonathan McAnultyDepartments of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.

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Abstract

Case Description—A 10-year-old spayed female Holland Lop–mix pet rabbit (Oryctolagus cuniculus) was evaluated because of purulent-hemorrhagic discharge from the right ear canal and a suspected mass within that ear canal.

Clinical Findings—Results of contrast-enhanced CT, video otoscopy, and histologic examination of endoscopic tissue biopsy samples indicated severe otitis media and externa and a benign trichoepithelioma of the right ear canal.

Treatment and Outcome—Total ear canal ablation and lateral bulla osteotomy were performed. Histologic examination of a surgical biopsy sample of the mass indicated malignant trichoepithelioma. Tumor recurrence was detected 22 weeks after surgery. The rabbit was euthanized 33 weeks after surgery because of the large size of the recurrent tumor and declining quality of life. Necropsy findings indicated a malignant trichoepithelioma with local and lymphatic invasion into the right mandibular lymph node.

Clinical Relevance—This was the first report of the clinical diagnosis, surgical treatment, and outcome for a domestic rabbit with a diagnosis of a malignant trichoepithelioma of the ear canal and associated otitis media and externa. Neoplasia should be included as a differential diagnosis for pet rabbits with otitis externa and media. Although such tumors are typically benign, trichoepitheliomas in rabbits can be malignant. Computed tomography and histologic examination of tissue samples were useful diagnostic techniques, but histologic examination of an endoscopic biopsy sample did not allow identification of malignant characteristics of the trichoepithelioma.

Abstract

Case Description—A 10-year-old spayed female Holland Lop–mix pet rabbit (Oryctolagus cuniculus) was evaluated because of purulent-hemorrhagic discharge from the right ear canal and a suspected mass within that ear canal.

Clinical Findings—Results of contrast-enhanced CT, video otoscopy, and histologic examination of endoscopic tissue biopsy samples indicated severe otitis media and externa and a benign trichoepithelioma of the right ear canal.

Treatment and Outcome—Total ear canal ablation and lateral bulla osteotomy were performed. Histologic examination of a surgical biopsy sample of the mass indicated malignant trichoepithelioma. Tumor recurrence was detected 22 weeks after surgery. The rabbit was euthanized 33 weeks after surgery because of the large size of the recurrent tumor and declining quality of life. Necropsy findings indicated a malignant trichoepithelioma with local and lymphatic invasion into the right mandibular lymph node.

Clinical Relevance—This was the first report of the clinical diagnosis, surgical treatment, and outcome for a domestic rabbit with a diagnosis of a malignant trichoepithelioma of the ear canal and associated otitis media and externa. Neoplasia should be included as a differential diagnosis for pet rabbits with otitis externa and media. Although such tumors are typically benign, trichoepitheliomas in rabbits can be malignant. Computed tomography and histologic examination of tissue samples were useful diagnostic techniques, but histologic examination of an endoscopic biopsy sample did not allow identification of malignant characteristics of the trichoepithelioma.

Contributor Notes

Dr. Drees' present address is Department of Clinical Sciences and Services, Royal Veterinary College, North Mymms, Hatfield, Hertfordshire AL9 7TA, England. Dr. Imai's present address is Comparative Pathology Laboratory, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

Address correspondence to Dr. Mans (cmans@vetmed.wisc.edu).