Use of the Argyrophilic Nucleolar Region Method for Cytologic and Histologic Examination of the Lymph Nodes in Dogs

Abstract

Abstract. Argyrophilic nucleolar organizer region (AgNOR) counts in cytologic and histologic lymph node samples from healthy dogs and dogs with lymphoma were compared. Control samples were taken from 10 Beagle dogs (six female and four male dogs, 1.5-2 years), and lymphoma samples were taken from 16 dogs. Cytologic samples were obtained by fine-needle aspiration and impression and histologic samples by excision or incisional biopsy. Altogether, 26 cytologic, 19 excisional, and 7 incisional biopsy samples were examined. Lymph nodes of controls showed a moderate inflammatory pattern; of the lymphoma cases, nine were lowgrade forms and seven were high-grade forms. Mean AgNOR counts per nucleus were determined. AgNOR counts were statistically different (P Ͻ 0.001) between controls and lymphoma cases in cytologic (1.35 and 3.59, respectively) and histologic (1.4 and 2.89, respectively) samples. In lymphoma cases, AgNOR counts in cytologic samples were higher than those in histologic samples by 0.81 (P Ͻ 0.001) and showed a linear relationship (r ϭ 0.6; P Ͻ 0.05) with the histologic counterparts in excisional biopsy samples. AgNOR counts in low-and high-grade lymphomas were significantly different (P Ͻ 0.05) in cytologic (3.21 and 4.08, respectively) and histologic (2.68 and 3.18, respectively) samples. In conclusion, AgNOR counts were higher in lymph nodes with lymphoma than in reactive nodes. In the case of dogs with lymphoma, AgNOR counts in cytologic samples were linearly related to excisional but not to incisional biopsy samples. Although AgNOR counts were different between cytologic and histologic samples, either sample type provided enough sensitivity to differentiate between high-and low-grade forms of lymphoma.

Argyrophilic Nucleolar Organizing Regions and Ki67 Equally Reflect Proliferation in Fine Needle Aspirates of Normal, Hyperplastic, Inflamed, and Neoplastic Canine Lymph Nodes (n = 101)

“…Here, a mean AgNOR count/cell of 1.36 6 0.19 (n 5 26) was obtained in normal dogs, which is consistent with the result reported previously (1.35 6 0.13 AgNORs/cell; n 5 10 ''control'' dogs). 5 It has to be considered, however, that only 2 normal dogs were included in this ''control'' group, whereas the remaining FNAs were obtained from each of 4 inflamed and hyperplastic lymph nodes. 5 A probable explanation for the similar results despite the different composition of the groups is that our investigations revealed no significant difference between normal lymph nodes, reactive hyperplasia, and lymphadenitis.…”

“…5 It has to be considered, however, that only 2 normal dogs were included in this ''control'' group, whereas the remaining FNAs were obtained from each of 4 inflamed and hyperplastic lymph nodes. 5 A probable explanation for the similar results despite the different composition of the groups is that our investigations revealed no significant difference between normal lymph nodes, reactive hyperplasia, and lymphadenitis. The evaluation of AgNORs in FNAs of human lymph nodes revealed a slightly lower mean AgNOR count in chronic lymphadenitis (1.16 6 0.1 AgNORs/cell; n 5 56) than in the dogs evaluated here (1.55 6 0.26 AgNORs/cell; n 5 31).…”

“…The concurrent investigation of lymph-node biopsy specimens and FNAs taken from 51 dogs with lymphoma revealed a good correlation between the results obtained from biopsy specimens and those obtained from a cytologic specimen (r 5 0.98). 4 However, in cytologic samples of lymphoid tissue, the AgNOR count was higher than in biopsy specimens in dogs 4,5 and people, 6 because nuclei in human 3-mm histopathologic sections do not have absolute AgNOR numbers. 7 The evaluation of FNAs of canine lymph nodes is considered to be less invasive, faster, and less labor intensive than biopsy.…”

“…6 The comparison between the AgNOR count/cell obtained from histology and cytologic specimen of 16 dogs with lymphoma and 10 control dogs revealed a linear relationship between cytologic and histopathologic results in the lymphoma group (r 5 0.60), but there was no correlation in the control group (r 5 20.47). 5 In both studies that evaluated AgNOR counts in FNAs of canine lymph node, different staining protocols were used, with durations of the silver stain that ranged from 30 minutes 5 to 45 minutes. 4 In both investigations, the AgNOR count was performed manually by light microscopy.…”

“…The AgNOR count alone was previously assessed in cytologic specimens obtained from 10 dogs with normal lymph nodes (n 5 2), lymphadenitis (n 5 4), and reactive hyperplasia (n 5 4) 5 ; however, the results were summarized as a ''control group,'' and only a small number of cases was evaluated. 5 Therefore, it was the aim of this study to assess the rate of proliferation based on the value of the AgNOR area/cell and the percentage of Ki67 positive cells against the known value of the AgNOR count/cell in FNAs obtained from dogs with normal lymph nodes, reactive hyperplasia, lymphadenitis, and lymphoma by using a standardized staining protocol 14,15 and automatic image analysis, as previously proposed. 10 A further objective was the evaluation of the potential diagnostic use of proliferation markers for detection of lymphoma, which has not been detailed before.…”