Prevalence and type of neoplastic disease were determined in 551 camelid submissions (368 alpacas [Lama pacos], 180 llamas [Lama glama], and 3 cases in which species was not identified) over a 5-year period. Forty neoplasms were identified in 38 animals (6.9%). Prevalence of neoplasia in llamas was higher (11%) than in alpacas (4.9%). Mean age of camelids with neoplasia was 9.42 +/- 4.9 years. Mean age of alpacas with neoplasia (5.48 +/- 3.7 years) was significantly less than of llamas with neoplasia (12.53 +/- 3.2 years; P < 0.001). Cutaneous and mucocutaneous fibroma/fibropapilloma was most common (10 animals), followed by cutaneous and mucocutaneous squamous cell carcinoma (6 animals), disseminated lymphoma (5 animals), and fibrosarcoma (4 animals). Four of 5 animals with lymphoma were alpacas, aged 0.21 to 4 years. Lymphoma occurred in 1 aged llama (15 years). Disseminated carcinoma and adenocarcinoma occurred in 4 llamas and 2 alpacas, and included biliary (2), gastrointestinal (2), mammary gland (1), and unknown (1) origin. Mean age of camelids with any type of carcinoma or adenocarcinoma (12.36 +/- 2.8 years) was significantly greater than that of camelids with lymphoma (4.24 +/- 6.2 years; P = 0.02). Results indicate that neoplasia is relatively common in camelids and that there are differences between llamas and alpacas as regards prevalence of neoplasia, tumor types, and age at diagnosis.

Malignant round cell neoplasia was identified in 12 llamas and 12 alpacas aged 0-23 years. Mean age of affected alpacas (3.1 years) was significantly less than that of affected llamas (8.0 years). Tumor cell morphology varied from large and often pleomorphic (11 tumors) to small and often homogeneous (13 tumors). Neoplastic lesions were multicentric in 12 cases. Other sites were gastric (5 cases), intra-abdominal (perirenal; 4 cases), intrathoracic (2 cases), and cervical (1 case). Immunohistochemistry with antibodies to CD79alpha, BLA36, and CD3 identified B-cell lymphoma (12 cases) and T-cell lymphoma (6 cases). Six tumors did not express any lymphoid marker and were further immunostained for neuron-specific enolase (NSE), synaptophysin, S-100, glial fibrillary acidic protein (GFAP), and chromogranin A. All 6 of these tumors were negative for GFAP and chromogranin A but expressed 1 or more of the neural markers NSE, synaptophysin, and S-100 and were classified as primitive malignant round cell tumors (PMRCT). Tumor types could not be distinguished on the basis of animal age, gross pathologic appearance, tumor morphology, or tumor location. All animals with lymphoma and 5 with PMRCT died or were euthanatized. One alpaca with a focal cervical PMRCT lived for at least 20 months after diagnosis. Results of this study indicate that malignant round cell tumors in llamas and alpacas are a heterogeneous group that cannot be distinguished on the basis of signalment, postmortem findings, or routine light microscopic findings. Immunohistochemistry is a valuable diagnostic procedure when evaluating malignant round cell neoplasia in llamas and alpacas.

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