Cytologic–histologic concordance in the diagnosis of neoplasia in canine and feline lymph nodes: a retrospective study of 367 cases

Abstract

Lymph nodes are frequently sampled in dogs and cats for the diagnosis of primary and metastatic neoplasia. We determined the accuracy of cytologic diagnosis in lymph nodes using histology as the gold standard. Lymph node reports (2001-2011) were retrospectively evaluated and diagnoses were categorized as neoplastic or non-neoplastic. Lymph nodes from 296 dogs and 71 cats included 157 (42.7%) non-neoplastic lesions, 62 (16.9%) lymphomas and 148 (40.3%) metastatic neoplasms. Cytology had a sensitivity of 66.6% [95% confidence interval (CI) 60.0-72.8%], specificity of 91.5% (CI 86.3-95.2%), and accuracy of 77.2% (CI 72.6-81.3%) for neoplasia. Likelihood of malignancy with a positive cytologic diagnosis of neoplasia was 93.0%. High proportions of false-negative results were found in mesenteric T-cell lymphoma (22/35, 63%, mainly cats), metastatic sarcoma (8/14, 57%) and metastatic mast cell tumour (15/48, 31%, mainly dogs). Factors contributing to discrepancies included well-differentiated lymphocyte morphology, focal distribution of metastases and poorly defined criteria for metastatic mast cell tumours.

Investigation of the utility of lymph node fine‐needle aspiration cytology for the staging of malignant solid tumors in dogs

“…The overall specificity of FNAC for the detection of tumor metastases found in our study (91%) was similar to that found in a previous study (91.5%); however, the overall sensitivity was superior in our study (81%) compared with this study (66.6%), which could be explained by the features of the previous study in which cytologic and histopathologic examinations were not always performed on the same LN, the time interval between cytologic and histopathologic examinations was up to 80 days, and cases of multicentric lymphoma were included . Nonetheless, our results concur that, although of high value and practicality, LN histopathologic examination cannot always be reliably substituted with FNAC.…”

“…The relatively low sensitivity of FNAC for detecting metastatic sarcomas in LNs (67%), also reported in a previous study, could be related, at least in part, to the poorly exfoliative nature of sarcomas, which limits the ability of FNACs to be used for metastatic sarcoma diagnoses . The relatively poor sensitivity of FNAC for detecting metastatic malignant melanomas in LNs (63%) has also been anecdotally reported .…”

“…We also aimed to elucidate the impact of nondiagnostic FNACs in the routine staging of canine solid tumors, a limitation that has not been assessed previously. Similarly, previous studies assessed only one LN for metastatic disease, which was usually the regional LN, although tumors can metastasize to several LNs, and sometimes “skip” the anticipated regional LN . In our study, we assessed several LNs and the impact that this such wider sampling had on staging results.…”

“…In another prospective study including 28 dogs and 3 cats with oral or maxillofacial neoplasms (10 squamous cell carcinomas, 6 fibrosarcomas, 5 melanomas, and 10 other tumors), the accuracy of FNAC for LN staging was 90.5% when compared with histopathology . In contrast, in a recent large retrospective study, the sensitivity and specificity of FNAC in the detection of LN neoplasia were 66.6% and 91.5%, respectively . However, the latter study was primarily designed to determine the agreement between FNAC and histopathology for diagnosing nodal neoplasia and was not specifically designed to assess the accuracy of FNAC in the setting of solid tumor staging …”

“…Only 2 relatively small prospective studies have assessed the accuracy of FNAC for LN staging in dogs, both finding good agreement with histopathology . A more recent, large retrospective study found that FNAC had poor sensitivity for detecting LN neoplasia; however, the authors did not design the study to assess FNAC in the setting of routine LN staging . We sought to assess the reliability of FNAC for LN staging in dogs with solid tumors, adding evidence to previously published studies.…”