Cytologic and histopathologic analyses were consistent with a round cell neoplasm; neoplastic cells showed nuclear immunoreactivity for MUM1 and diffuse cytoplasmic reactivity for CD3.
Polymerase chain reactions performed on fixed and fresh tissue identified a clonal rearrangement with an IgH primer set.
An extramedullary plasmacytoma (EMP) was confirmed by cellular morphology and molecular diagnostics.
Following an objective response to chemotherapy, the dog was euthanized 8 months after diagnosis, and a postmortem examination confirmed the clinical findings.
This is the first reported case of a monoclonal gammopathy secondary to a gastric EMP coupled with aberrant expression of CD3 in an aggressive plasmacytic tumor, and highlights the utility of molecular diagnostics for classifying atypical hemolymphoid neoplasms.
Source: Atherton, M. J., Vazquez-Sanmartin, S., Sharpe, S., Waugh, E. M. and Morris, J. S. (2017), A metastatic secretory gastric plasmacytoma with aberrant CD3 expression in a dog. Veterinary Clinical Pathology. doi: 10.1111/vcp.12503
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