Solitary plasmacytoma of bone in two successfully treated cats

Abstract

This is the first report of feline solitary plasmacytoma of bone. We describe the clinical, clinico-pathological, radiographic and pathological findings of two successfully treated cats with long-term follow-up. The first case presented with spinal pain and neurological deficits. Radiographs demonstrated sclerosis of lumbar vertebra L6 and a myelogram confirmed interference to flow of contrast in the L4-7 region. A biopsy of L6 revealed neoplastic plasma cell infiltration. There was no evidence of paraproteinaemia on serum protein electrophoresis. The cat underwent hypofractionated megavoltage radiotherapy. Clinical signs resolved completely and 4 years after diagnosis the cat remains well and has no electrophoretically detectable paraproteinaemia. The second case presented with neurological deficits of the tail and spinal radiographs revealed extensive osteolysis of the sacrum. A biopsy of sacral bone demonstrated neoplastic plasma cell infiltration. The animal was normoglobulinaemic. The cat improved clinically with induction chemotherapy (melphalan and methylprednisolone). The same chemotherapeutics were continued at maintenance doses for 4.3 years, at which time there was recurrence of neurological deficits and a palpable sacral mass. Cytological examination of a fine needle aspirate confirmed recurrence of plasma cell neoplasia. A low concentration monoclonal paraproteinaemia was detected. Vincristine was administered resulting in resolution of neurological deficits and a palpably smaller sacral mass. Eighteen months into vincristine therapy, there was recurrence of clinical signs and the cat was euthanased, more than 6 years after the initial diagnosis.

Fine needle aspiration cytology in feline skeletal muscle as a diagnostic tool for extramedullary plasmacytoma

“…Only through palpation we noticed the presence of a soft consistency nodule. There has been a report about an animal presenting hind limb ataxia, decreased tail movements, and muscular weakness, as well as a painless mass in the sacral dorsal region (Mellor et al, 2007). As the cat in the study mentioned had free access to the street and was predisposed to fights for being a noncastrated male young cat, there was an initial suspicion of muscle trauma.…”

“…Sometimes the laboratory tests, such as CBC and serum chemistries, do not reveal changes resulting from plasmacytoma, except for the increased value of proteins (Mellor et al, 2007). The radiographic examination can help in cases where there is bone involvement.…”

“…There are few reports of plasmacytoma in which the diagnosis was made by FNAC with subsequent ratification by histopathology (Mellor et al, 2007;Igase et al, 2015). This report aims to describe the case of an 8-month-old, FeLV-positive, feline diagnosed by FNAC, with extramedullary plasmacytoma in the semimembranosus muscle, making this case unusual.…”

“…The plasma cell neoplasms are classified as multiple myelomas, solitary plasmacytoma, and extramedullary plasmacytoma (Majzoub et al 2003;Radhakrishnan et al, 2004;Mellor et al, 2007). This kind of neoplasm is considered rare in cats (Majzoub et al, 2003).…”

“…However, literature often reports plasmacytoma cases with a primary diagnosis made by histopathology (Majzoub et al, 2003;Mellor et al, 2007;Adelman et al, 2014). There are few reports of plasmacytoma in which the diagnosis was made by FNAC with subsequent ratification by histopathology (Mellor et al, 2007;Igase et al, 2015).…”