The enzootic form of bovine lymphosarcoma is associated with BLV infection and is the most common neoplastic disease of cattle.1 Antemortem diagnosis of EBL is sometimes difficult in cattle in which nonspecific clinical findings are encountered. Because of the grave prognosis for the individual animal and possible implications for the herd related to transmission of BLV, it would be advantageous to obtain a definitive diagnosis prior to necropsy or slaughter. In some instances, genetically valuable animals receive an incorrect diagnosis of enzootic lymphosarcoma on the basis of vague clinical findings and positive results of a gp51 BLV antigen test, when in fact, only approximately 1.7% of cattle with positive test results for BLV develop tumors.2
Presently, antemortem diagnosis of EBL is based largely on clinical signs aided by serologic and sometimes hematologic and serum biochemical testing. Clinical signs of EBL are dependent on the organs involved and can be nonspecific as the disease process proceeds. Peripheral lymphadenopathy is a common clinical manifestation of EBL but alone is not sufficient for definitive diagnosis because inflammatory processes can also result in lymph node enlargement. Although a positive serologic test result for the BLV gp51 antigen has little correlation with EBL, a negative gp51 test result is helpful in ruling out EBL because only approximately 1 in 10,000 cattle with EBL have negative results for BLV.2 Tests for the p24 antigen may also aid in determining the likelihood of an animal having EBL. If an animal has positive results for gp51 and p24 antigens, the probability for EBL is increased; however, this is still not definitive because some animals without EBL may have positive results for both antigens as well.2 In addition, few laboratories have the capability of performing p24 antigen testing.1
Hematologic findings can be suggestive of a diagnosis of EBL. Detection of atypical or immature lymphocytes in circulation, with or without lymphocytosis, is common but not specific for EBL. Lymphoblastic leukemia, with large numbers of circulating lymphoblasts, is seen in a minority of cases.3 Total serum activities of LDH are reportedly greater in cattle with enzootic lymphosarcoma, compared with clinically normal cattle.4 In addition, changes in distribution patterns of LDH isoenzymes occur that may be indicative of EBL.4 However, other processes such as musculoskeletal or liver disease may result in similarly high activities in LDH, and changes in the distribution of LDH isoenzymes can occur over time in clinically normal animals.5 Although clinicians have the ability to correlate laboratory data and clinical findings and make a tentative diagnosis of EBL, a definitive antemortem test is lacking.
In dogs, FNA with subsequent cytologic examination of enlarged peripheral lymph nodes can be diagnostic. Aspirates composed of a predominance of large lymphoblasts are indicative of lymphoma.6 In cattle, lymph nodes reacting to infection and those infiltrated with neoplasia may appear similar, making differentiation difficult.1 It would be advantageous to the bovine clinician to determine the value of performing biopsies and FNA of enlarged lymph nodes in the attempt to arrive at a definitive antemortem diagnosis of EBL. However, to the authors' knowledge, reports describing the findings of biopsy specimens and FNA of enlarged bovine peripheral lymph nodes from cases of enlargement caused by inflammation and neoplasia are lacking.
In the study reported here, the objective was to determine whether CNB and FNA of enlarged peripheral lymph nodes obtained antemortem could be used to distinguish between inflammation and EBL in cattle. Our hypothesis was that by using a CNB instrument, more of the lymph node's architectural features would be available for histologic assessment of an effacing neoplastic infiltrate, compared with that obtained with FNA, and that FNA would have limited value in differentiating between inflammation and neoplasia as the cause of lymph node enlargement.
Bovine leukemia virus
Enzootic bovine lymphosarcoma
Core needle biopsy
Ocular squamous cell carcinoma
Jorgenson Laboratories, Loveland, Colo.
EpiCalc 2000, version 1.02, Brixton Health, Llanidloes, UK. Available at: www.brixtonhealth.com/. Accessed Nov 28, 2005.
Decision/test relation calculators, Department of Family and Preventive Medicine, The University of Oklahoma Health Sciences Center, Oklahoma City, Okla. Available at: www.fammed.ouhsc.edu/robhamm/cdmcalc.htm. Accessed Dec 2, 2005.
SPSS for Windows, version 13.0, SPSS Inc, Chicago, Ill.
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Scopa CD, Koukouras D, Spiliotis J, et al. Comparison of fine needle aspiration and tru-cut biopsy of palpable mammary lesions. Cancer Detect Prev 1996;20:620–624.