Solitary osseous plasmacytoma of a lumbar vertebrae with systemic involvement in a dog

ABSTRACT

Background: Myeloma-related disorders are characterized by proliferation of neoplastic plasma cell or immature immunoglobulin secreting B-lymphocytes, and include multiple myeloma, M-macroglobulinemia and extra-medullary plasmacytoma(cutaneous or extra-cutaneous). Solitary osseous plasmacytoma (SOP) is considered an unique entity among extra-medullaryextra-cutaneous plasmacytoma. It is an unusual neoplasia in dogs, predominantly found in middle-aged to older animals,with a higher incidence in bones of axial skeleton. Dogs with vertebral SOP present neurological signs related to spinalcord compression, but progression to multiple myeloma is related to a poor outcome. As in humans, progression to multiple myeloma occurs in most cases, although it may take months or years from its initial presentation. SOP’s biologicalbehaviour, incidence and prognostic are rarely documented. Chemotherapy with melphalan and prednisolone representthe most used protocol for multiple myeloma. However, in SOP, the combination of chemotherapy with local approachesis controversial before the evidence of systemic disease. This paper aims at reporting a case of SOP in a lumbar vertebraeof a dog, with systemic involvement.Case A 11-year old male mixed breed dog was attended presenting muscle weakness, lethargy, anorexia, adipsia and intense pain manifestation. The dog also presented multiple skin nodules, previously diagnosed as a plasmacytoma, throughcytology. The dog’s poor clinical condition and aggressive temper, associated with suspicious of an advanced myelomarelated disorder, resulted in the decision for humanized euthanasia. At necropsy, a pale, friable and hemorrhagic masswas identified on the L3 lumbar vertebrae, associated with an osteolytic bone lesion and spinal cord compression. Histopathological analyses revealed proliferation of plasma cells, with pale perinuclear halo, moderate cellular pleomorphism,10 binucleated cells and 10 mitotic figures per 10 high...