This study and previous studies indicate that camelids with MRCT can present with a variety of clinical signs and laboratory findings, and that the clinical course is variable (6
). Tumors occur at all ages and many affected animals are less than 4 y of age. Tumors are particularly common in young alpacas. No other significant differences between alpacas and llamas were detected.
As in prior reports, presenting complaints in this study included anorexia, weight loss, weakness, and respiratory distress (6
). Peripheral lymphadenomegaly was the most specific finding, and palpable lymphadenomegaly was detected in 9 of 10 camelids with MRCT in a prior study (6
). In the current study population lymphadenomegaly was detected clinically in only 4 cases, but was detected at necropsy in 7 animals (10
). Findings indicate that careful clinical evaluation of peripheral lymph nodes is an important part of camelid physical examination.
Clinicopathologic abnormalities were most often non-specific (18
). Azotemia only rarely reflected renal neoplasia, and increase in serum GGT or aspartate aminotransferase (AST) occurred in animals with neoplasia involving the gastrointestinal tract as well as in animals that had tumor in the liver. Hypokalemia was a common finding, which most likely reflects anorexia (18
). Hyperglycemia was also common, but camelids are very prone to stress hyperglycemia (18
), and an increased serum glucose level is not considered to be related to underlying MRCT in these cases. Low serum glucose levels are significant, and the 2 animals with hypoglycemia died within 2 d of examination. These animals had extensive hepatic neoplasia. Hypoglycemia associated with MRCT may be an indicator of a poor prognosis, but additional studies are needed. Hypercalcemia may be associated with lymphoma (20
), but was not detected in any case. Lymphocytosis was detected in only 1 animal in this study and in 3 animals in previous studies (6
), suggesting that lymphocytosis is uncommon in camelids with MRCT. Cattle with bovine leukemia virus associated lymphoma often have persistent lymphocytosis (20
). There has been no evidence of a viral cause of lymphoma in camelids, and the variety of cell types of MRCTs in camelids (B-cell lymphoma, T-cell lymphoma, and PMRCT) does not support a viral cause for MRCT in these species.
Ultrasonography of 6 animals in this study detected evidence of neoplasia in 4 cases but did not detect masses in 1 animal with gastric lymphoma, or in 1 with multicentric lymphoma. The cranial location of gastric neoplasia, particularly that involving compartment 1, may make ultrasonographic detection of gastric MRCT difficult. Cytologic evaluation of thoracic or abdominal fluid was diagnostic in 3 of 4 cases examined in this study. Cytologic evaluation of enlarged peripheral lymph nodes was performed in 2 cases and provided a diagnosis of MRCT in both cases. Cytologic evaluation of thoracic, abdominal, or cerebrospinal fluid was reported to be diagnostic in 4 previous cases of MRCT in camelids (6
). Biopsy of enlarged lymph nodes or liver resulted in diagnosis of MRCT in 5/5 cases. Results of the current study and previous studies indicate that ultrasonographic examination and cytologic evaluation of fluid, peripheral lymph nodes, or masses, and evaluation of biopsy samples of liver or other involved organs are useful for diagnosis of MRCT in camelids.
Animals up to 2 y of age often had a course of clinical disease of ≤ 2 wk. In humans, MRCT of childhood often has a poor prognosis, and tumors often metastasize quickly (5
). This study suggests that MRCT affecting camelids up to 2 y of age is associated with a worse prognosis than MRCT in older camelids, but additional studies are needed.
The rapid clinical course seen in most of the animals, and the size of the masses found on necropsy, suggest that many of the animals were in an advanced stage of disease before they showed clinical signs. It is more effective to diagnose MRCT in camelids based on physical and diagnostic findings than from clinical signs. To date, only Cebra et al (6
) have reported results of chemotherapy in a camelid. The case was a 1-year-old llama with a diagnosis of lymphoma. The animal showed improvement for 1 d, then rapidly deteriorated. The likelihood of effective chemotherapy will be increased by early tumor detection.
Based on results of this study, a yearly physical examination in adult camelids, and more frequent examination of camelids up to 2 y of age, are recommended, as this should increase the likelihood of detecting disease early in its course. Physical examination should include a thorough palpation to detect peripheral lymphadenomegaly. Mandibular and inguinal lymph nodes in particular should be examined. Routine clinicopathologic studies may not reveal a specific change, but will provide indicators of the overall health status of the animal, and should be included in the regular physical examinations. If abnormalities are detected, especially hypoalbuminemia, anemia, leukocytosis, abnormal liver or kidney values, or leukocytosis, thoracic or abdominal ultrasound may be warranted. The liver is often involved in camelids with MRCT (6
), and careful ultrasonographic evaluation of this organ is recommended. If abnormalities consistent with neoplasia are detected with diagnostic imaging, biopsy or cytologic evaluation of the lesions should be done. Abdominal or thoracic effusions should be evaluated cytologically. In cases of MRCT, immunophenotyping with specific antibodies for B-cells, T-cells and, when indicated, primitive neuroectodermal cells should be performed. Early detection of MRCT and accurate determination of tumor cell type may allow for development of chemotherapeutic regimens for treatment of MRCT in llamas and alpacas. CVJ