Extramedullary plasmacytoma in a captive collared peccary (Pecari tajacu)

Abstract

Abstract: An extramedullary plasmacytoma case in a captive collared peccary (Pecari tajacu) is reported. The animal, a female aging three years old, had a medical history of diffusely distributed skin and mucocutaneous junction lesions, associated with swollen lymph nodes. Clinical examination and complementary exams (complete blood count, biochemical analysis, skin scraping to search mites and fungal culture) were performed. Thirty days after examination, the animal died. At necropsy, multiple consistent nodules, aseptic pustules and swollen lymph nodes were found. On histological exams of the skin and oral mucosa, we observed a large number of round cells forming masses organized in nests, sheets, and cords of cells in a well-vascularized fibrovascular tissue. Neoplastic plasma cells infiltrated between the fibers and the lamina propria of smooth muscle. Spaces among the cell masses were filled with some eosinophil and fluid. Most of the cells were well differentiated, presenting a perinuclear clear zone. In some points, the cells were pleomorphic. The plasma cells presented eccentric, basophilic and spherical nuclei, showing a dense to organized chromatin with distinct nucleoli. Binucleate cells were observed, but multinucleated giant cells were rare. Oral mucosa and lymph nodes tested by immunohistochemical analyses were positive for Mb-1, with a multifocal distribution. In regard to Bcl-2, the neoplastic cells were intermittent weakly positive. So, an extramedullary plasmacytoma was diagnosed in the collared peccary considering the location, the histopathological and immunohistochemical findings.