Chromogenic in situ hybridization for the detection of lambda and kappa immunoglobulin light chains as a potential auxiliary diagnostic technique in canine plasmacytomas

A clonality assay in canine B cell tumors targeting the immunoglobulin light chain lambda locus

Clonality assays for antigen receptor rearrangement have been used as adjunct examinations of lymphoproliferative diseases. These assays have been useful for differentiation between inflammation and clonal expansion of lymphocytes. Whereas the immunoglobulin heavy chain (IGH) and immunoglobulin light chain kappa (IGK) loci have been targeted in canine clonality assays previously, the immunoglobulin light chain lambda gene (IGL) locus has not yet been investigated. This study aimed to evaluate the usefulness of clonality assays in dogs using IGL. Canine diffuse large B cell lymphomas (DLBCL), cutaneous plasmacytomas, and pathologically diagnosed lymph nodes without lymphoma, were used in this study. Genomic DNA was extracted from formalin-fixed paraffin embedded sections. Sequences of IGLV and IGLJ were obtained from the ImMunoGeneTics database. Several primers against IGLVs and IGLJs were designed in the regions showing homology, by alignment of the gene segments. Products of polymerase chain reaction were analyzed on a capillary electrophoresis. In total, 20 of 23 cases of DLBCL showed clonality (87.0 %), whereas 8 of 30 cutaneous plasmacytomas were clonal (26.7 %). One of 23 lymph nodes without lymphoma showed clonality, thus the specificity was 95.7 %. These data indicate that the IGL locus could be a target for canine clonality assays and that the sensitivity of IGL-based clonality assays in cutaneous plasmacytomas was lower than that in DLBCL.

Multiple myeloma involving the gastrointestinal tract in an English Springer Spaniel

A 10‐year‐old, entire male, English Springer Spaniel was referred for evaluation of weight loss, polyuria, polydipsia and gastrointestinal tract signs including melena/haematochezia for the previous six months. Results of serum protein electrophoresis, urine analysis, computed tomography of the thorax/abdomen, bone marrow aspiration and core biopsy, and splenic and mesenteric lymph node cytology were consistent with multiple myeloma. Endoscopically obtained gastrointestinal tract biopsies identified marked plasma cell infiltration within the duodenum, ileum and colon; immunohistochemistry showed positive labelling to MUM1 and Lambda confirming clonal plasma cell involvement. The dog entered complete clinical remission seven weeks after starting a melphalan/prednisolone protocol. The dog was euthanised 475 days after starting treatment due to cervical pain and collapse. At the time of euthanasia, blood work was not supportive of a relapse of multiple myeloma. To the authors’ knowledge, this is the first report of multiple myeloma involving the gastrointestinal tract in a dog.