Pathologic and immunophenotypic characterization of 26 camelid malignant round cell tumors.

Lymphoma and/or leukemia was diagnosed in 26 camelids (20 alpacas and 6 llamas) out of 110 camelid neoplasia archived January 1995 through January 2012 at the Colorado State Veterinary Diagnostic Laboratories (CSU-VDL). Some of the tumors presented a diagnostic challenge because they could not be distinguished on the basis of gross or microscopic morphology. Immunohistochemistry using a T-cell marker (cluster of differentiation [CD]3), a B-cell marker (paired box protein [PAX]-5), a leukocyte integrin beta-2 marker (CD18), and a neuroendocrine marker (synaptophysin) was employed to help differentiate between lymphoma and other malignant round cell tumors. Alpaca lymphomas presented as either juvenile disseminated lymphoma in crias ≤ 2 years of age (n = 8) or adult multicentric lymphoma and/or leukemia (n = 12). Lymphomas in alpacas were of T-cell origin (n = 13), non-B-cell, non-T-cell origin (n = 4), B-cell origin (n = 2), or myelogenous leukemia (n = 1). Abdominal organs, predominantly the liver, were commonly involved in both the crias and adult alpacas. Lymphomas in llamas presented as either adult multicentric lymphoma of B-cell origin in animals younger than 7 years of age (n = 2), or T-cell lymphoma (n = 2), and non-B-cell, non-T-cell lymphoma (n = 1) in animals 7 years of age or older. The thorax was commonly involved in llamas, with infiltration of neoplastic cells into hilar and mediastinal lymph nodes. A rare type of lymphoma diagnosed in the llamas was cutaneous, epitheliotrophic T-cell lymphoma (n = 1).