Five types of lymphoid neoplasms in calves are described. Four cases with clinicopathologic features of the "calf form of lymphoma" were diagnosed as precursor B or T lymphoblastic leukemia. These neoplasms were positive for terminal deoxynucleotidyl transferase (TdT), a marker for immature lymphocytes. The fifth case (thymic B cell lymphoma) was also TdT positive, but was characterized by massive neoplastic involvement of the thymus. The sixth case involved bovine leukemia virus (BLV). As in the majority of previously reported BLV-associated cases, the neoplastic cells expressed CD5, and atypical giant cells were detected. Instead of enzootic bovine leukosis, in which at least two immunophenotypically distinct entities are included, a diagnosis of BLV-associated pleomorphic B-1 B cell lymphoma was made. The last case, involving an epitheliotropic γδ T cell lymphoma, was characterized by epitheliotropism in the gastrointestinal tract and WC1 expression. Since several histologic types of lymphoid neoplasm occur in calves, the term "calf form of lymphoma" should be abandoned for accurate diagnosis.

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