Cutaneous Plasmacytomas in Dogs: A Morphologic and Immunohistochemical Study

Abstract

Forty-nine cutaneous plasmacytomas in 46 dogs were studied. Tumors occurred at solitary sites in middle-aged to old dogs (mean age, 9.7 years) and most commonly involved the skin of the digits, lips, and ears. Initial diagnosis was made on the basis of light microscopic morphologic findings. Tumors were graded according to the extent of cellular differentiation and immunoreactivity to a panel of immunohistochemical markers (cytokeratins, canine IgG F[ab]2, neurofilament, neuron-specific enolase, S-100 protein, and vimentin). Immunoreactivity was limited to antibodies directed at canine IgG F(ab)2 and vimentin. Vimentin immunoreactivity was usually greater than that of canine IgG F(ab)2, but there was no correlation between immunoreactivity and histologic grade of the tumors. Thirty-six of 39 dogs (92.3%) followed (mean follow-up, 13 months) were cured by surgical excision. The results of this study indicate that canine cutaneous plasmacytomas are benign neoplasms that should be included in the differential diagnosis of cutaneous round cell tumors in dogs.

Histomorphological and immunohistochemical characterization of 172 cutaneous round cell tumours in dogs

“…Vimentin is a marker of mesenchymal cells and is expressed in the TVT (Pereira et al 2000), in the MCT (Jakab et al 2009, Lin et al 2010, in the PCT (Baer et al 1989, Schrenzel et al 1998) and in the LHS (Azakami et al 2006). In this study, the tumours deϐined as TVT by IHC were positive for vimentin in 100% (6/6) of the cases and positive for CD45 in 28.6% (2/7) of the cases.…”

Identification of Immunoglobulin Light Chains in Canine Extramedullary Plasmacytomas by Thioflavine T and Immunohistochemistry

“…18,19 Previous studies of canine EMP have used a variety of immunohistochemical markers for diagnostic purposes and have determined that canine EMPs are of plasma cell origin. 1,13,20,24 The neoplastic nature of the tumors was confirmed by the identification of a monoclonal expression of immunoglobulin light chains. l3 In this study, the tumors predominantly expressed λ light chains.…”

“…Other round cell neoplasms (lymphosarcoma, histiocytoma, and mastocytoma) were negative with thioflavine T, indicating that positive staining with thioflavine T was specific for plasma cells (neoplastic and inflammatory). This study confirms by immunohistochemistry that canine extramedullary plasmacytomas disproportionately express λ light chains and establishes thioflavine T staining as a rapid histochemical method for diagnosis of these tumors.The morphologic, clinical, and biological features of canine extramedullary plasmacytoma (EMP) have been reported 1,13,16,17,20,24 Most dogs were aged adults, and tumors developed most commonly on the mucocutaneous junction of the mouth, the skin between the digits, and on the external ear. 1,24 More than 90% of the dogs with cutaneous EMP were cured by surgical excision, indicating that these tumors were most likely benign.…”

“…The morphologic, clinical, and biological features of canine extramedullary plasmacytoma (EMP) have been reported 1,13,16,17,20,24 Most dogs were aged adults, and tumors developed most commonly on the mucocutaneous junction of the mouth, the skin between the digits, and on the external ear. 1,24 More than 90% of the dogs with cutaneous EMP were cured by surgical excision, indicating that these tumors were most likely benign.…”

“…1,24 More than 90% of the dogs with cutaneous EMP were cured by surgical excision, indicating that these tumors were most likely benign. Multiple EMP were found in a small percentage of dogs but were not associated with progression to multiple myeloma.…”