Extramedullary plasmacytoma of the oral cavity metastasising to both kidneys in a dog

Abstract

Background: Most extramedullary plasmacytomas (EMPs) aresolitary and located in the head and neck region. They may also occur in the visceral parts of the body.Objectives: Here, we report a case of oral EMP followed by neoplastic plasma cell metastasis to both kidneys in a neutered male Pomeranian. Methods: Oral plasmacytoma recurred 11 months aftersurgical removal of an oral mass and partial maxillectomy was performed. Eighteen months after partial maxillectomy, neoplastic masses were detected in both kidneys on computed tomography.The dog died 12 months after detection of bilateral kidney neoplasms. The resected neoplastic masses were routinely processed for histopathological observation and immunohistochemistry against pan-cytokeratin, desmin, CD3, and MUM-1. Results:The recurred mass mainly consisted of well-differentiated plasma cells and contained a small portion of aggressive cells with malignant features. Monoclonal gammopathy was not observed on serumelectrophoresis performed to exclude multiple myeloma. The mass was composed of plasma cells with high nuclear pleomorphism and abundant mitotic figures. The neoplasm stained positive for MUM-1 with a more aggressive morphology than in oral EMP. Conclusion:Based on serum biomarker and pathological observations, a diagnosis of recurrence and metastasis of oral-to-renal EMP was established. To the best of our knowledge, metastasis of oral EMP into the bilateral kidneys, as described in the current case, has not been previously reported in dogs.

Cutaneous Plasmacytoma with Systemic Metastases in a Cape Serotine Bat (Laephotis capensis)

“…In this case, report, however, the mitotic count was high, and the presence of marked nuclear pleomorphism with occasional bi- and multinucleation was also observed, suggesting an aggressive tumour. Indeed, a report of a canine oral EMP that metastasised to both kidneys found the tumour cells showed aggressive features, including high nuclear pleomorphism, multinucleated cells, and a high number of mitotic figures [ 19 ]. Consistent with this, the EMP in this case showed evidence of systemic metastases, with neoplastic cells in circulation, specifically in the liver and bone marrow, as well as a locally extensive infiltration of the spleen.…”

“…MUM1, encoded by the IRF4 gene, is a regulatory protein involved in the differentiation of B-lymphocytes to plasma cells and is required for immunoglobulin light-chain rearrangement. It is useful to identify plasmacytomas, MMs, and B-cell lymphomas in both canines and felines [ 6 , 14 , 19 ]. Indeed, of the B-cell markers commonly used in veterinary species, MUM1 is the preferred plasma cell marker for normal and neoplastic plasma cells, with one study reporting 84% of plasma cell tumours showing positive labelling, compared to 59/105 (56%) for CD79a and 21/108 (19%) for CD20 [ 39 ].…”

“…In dogs, most cutaneous EMPs are benign solitary nodules, and complete excision is usually curative, although recurrence has been reported in some cases [ 3 , 6 ]. Indeed, although there have been reports of metastasis in a few cases of canine EMPs, these were located in the gastrointestinal tract and oral cavity, thus not of cutaneous origin [ 16 , 17 , 18 , 19 ]. By contrast, one study of cutaneous EMPs in felines found 4/11 (36%) cases developed metastasis [ 14 ], and metastasis has also been reported in EMPs from other sites [ 8 ].…”