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Extramedullary laryngeal plasmacytoma in a dog
A I Witham1, A F French, K E Hill
1Institute of Veterinary, Animal and Biochemical Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. awitham@unimelb.edu.au
Case History:
An 8-year-old, female, spayed Border Collie presented with a 3-week history of coughing, choking and haemoptysis.
Clinical Findings:
Inspiratory stridor was evident on clinical examination. Cervical radiographs revealed a round soft-tissue mass on the dorsal aspect of the epiglottis. A laryngeal mass was evident on examination under anaesthesia, and an incisional biopsy was obtained. Histopathology revealed a dense proliferation of neoplastic round cells morphologically consistent with plasma cell origin. Immunohistochemisty results were negative for CD3 (T cell marker) and positive for CD79a (B cell marker), resulting in a diagnosis of extramedullary plasmacytoma. The patient was treated with melphalan and prednisolone; clinical signs resolved within 1 week and the mass was no longer evident on laryngoscopy after 1 month of treatment. After 6 months of chemotherapy, the laryngeal mass recurred and euthanasia was requested. There was no evidence of systemic spread on post-mortem examination.
Diagnosis:
Solitary extramedullary plasmacytoma of the canine larynx.
Clinical Relevance:
Respiratory extramedullary plasmacytomas are extremely rare with only one laryngeal and two tracheal cases previously reported. This is the first published report of a laryngeal plasmacytoma that recurred despite combination chemotherapy with melphalan and prednisolone.
