Cytologic and Immunophenotypic Investigation of Lymphohematopoietic Neoplasms in Cattle

Abstract

Ten cases of bovine lymphohematopoietic neoplasms were investigated histologically, histochemically, and immunohistochemically, and were classified into eight histologic types on the basis of the origin and morphology of tumor cells. Case 1, a precursor B lymphoblastic leukemia, was positive for CD79a and terminal deoxynucleotidyl transferase. Case 2, a thymic B cell lymphoma, was also positive for these markers, but there were cytologic differences between the two cases. Cases 3-5 were diagnosed as pleomorphic B cell lymphomas, which were characterized by cytologic pleomorphism and expression of CD79a and CD5, and were etiologically associated with bovine leukosis virus (BLV). A case of diffuse large B cell lymphoma of the cerebrum (case 6) also showed a positive result for CD79a and CD5. However, the lymphoma was composed of a homogeneous population of large neoplastic cells, and was considered to be unrelated to BLV. The other B cell cases were categorized into immunoblastic (case 7) and lymphoplasmacytic (case 8) lymphomas, in which immunoglobulin-producing lymphoma cells were observed. In a cutaneous γδ T cell lymphoma (case 9), the neoplastic cells cytologically resembled those in case 6, but expressed CD3 and WC1. In case 10, an acute basophilic leukemia, some leukemia cells had intracytoplasmic granules that were metachromatic and tryptase positive but negative for naphthol AS-D chloroacetate esterase. Bovine lymphohematopoietic malignancies are classifiable into discrete histologic types according to immunophenotype. The classification is more scientific than the traditional one, the latter being based on the age of affected animals and/or the site of tumor formation.

Cytology of B Cell Lymphomas in Cattle Infected with Bovine Leukosis Virus

“…In case 17, conversely, immunoblastoid and plasmacytoid cells showed IgG production. Similar cells were observed in lymphoplasmacytoid and lymphoplasmacytic lymphomas in BLV-negative cattle 6,13 . As in the former, CD5 was expressed on neoplastic cells in case 17, and a diagnosis of lymphoplasmacytoid lymphoma was made 6 .…”

“…This suggests that the CD5 expression tends to be lost or greatly diminished during neoplastic transformation. Since similar phenomena were observed for other lymphocyte markers in bovine lymphoid neoplasms 9,13 , it is possible that cases with few positive cells are mistakenly judged negative.…”

“…Although clinical abnormalities were noted in case 17, the severe involvement of the spleen, liver and peripheral blood and the absence of extranodal tumor masses were reminiscent of a lymphoma with a marked tendency to become leukemic 6 . There were no Ig-producing lymphoma cells in cases 1-16, which is an important feature of pleomorphic B cell lymphoma 13 . In case 17, conversely, immunoblastoid and plasmacytoid cells showed IgG production.…”

“…Similar to the reports for pleomorphic B cell lymphoma 1,9,13. , in this study the main cytological findings from cases 1-16 were pleomorphism and atypia, which are not so prominent in other histological types of lymphoid neoplasms 1,2,[6][7][8][9][10]13,14,17,18 . Such features were considered characteristic of the majority of lymphoma cases truly associated with BLV.…”

“…These classifications are based on the cell size and/or nuclear cleavage and fail to distinguish between BLV-positive and negative cases. In contrast, some cases of BLV-positive lymphoma, which were diagnosed as pleomorphic B cell lymphoma based on pleomorphism and atypia 1,9.13 , were cytologically distinct from other lymphoid malignancies 1,2,[6][7][8][9][10]13,14,17,18 . In this paper, we describe the histology and immunohistochemistry of B cell lymphomas in 17 cows having tested positive for BLV by nested polymerase chain reaction (PCR).…”