Imunofenotipagem comparada dos plasmocitomas extramedulares, histiocitomas e linfomas cutâneos em cães

Abstract

The literature about canine extramedullary plasmacytoma (CEP) is wide and contradictory. Due its great morphological variety, this neoplasm is commonly confused with others benign and malignant tumors in histopathologic diagnostic routine; mainly with Canine Cutaneous Histiocytoma (CCH), Canine Histiocytic Sarcoma (CHS) and Canine Lymphoma (CL). Aiming to compile information to investigate and clarify aspects regarding the immunophenotyping of CEPs, immunohistochemistry tests were performed in tissue microarray (TMA) with 2mm colors, using the conventional markers CD79a (in duplicate), CD3 (in duplicate), MUM1 (in duplicate), Iba1 and immunoglobulin λ and κ light chains in 39 CEPs, 27 CCHs and 8 CLs. For comparison and control purposes, the study also included samples from 2 CHSs, 2 cutaneous mast cell tumors (MCT), 2 oral melanomas and 1 multiple myeloma; in addition to normal and reactive tissues from canine lymph nodes, spleen, bone marrow and skin. Furthermore, an analysis unprecedented was carried out with the antibody anti- Interleukin 3 alpha receptor (CD123) applied in dogs. The CD123 has been widely studied in human medicine as an efficient marker of some lymphoid neoplasms, mast cells and blastic plasmacytoid dendritic cells, but it is practically unexplored in medicine veterinary. To evaluate the efficiency of the tissue microarray (TMA) for some markers used, a pilot immunohistochemical study was carried out in the conventional histological sections with MUM1 and CD79a in 27 samples of CEPs and 10 of CCHs, with antibodies anti-CD3 and CD79a in 8 samples of CLs (5 cutaneous and 3 nodal) and with anti-CD123 in samples of 7 CEPs and 2 CCHs. The mainly conclusions found out were: 1) MUM1 is very sensitive (89.7%) to detect CEPs and efficient to differentiate CEPs from histiocytic neoplasms; 2) T-cell lymphomas can to express MUM1; 3) CD123 is expressed in CEPs, MCCs and CHSs, in addition to normal plasmocytes, endothelium and possibly by canine plasmacytoid dendritic cells; 4) CD123 antigen expressions in malignant neoplasms such as MCC and CHS must be further investigated; 5) The Iba1 antibody had 100% sensitivity to detect CCHs and CHSs, being very specific for these neoplasms.