Palpation and Computed Tomography as Surrogates for Lymph Node Cytology in Dogs With Sinonasal Cancer

In dogs with sinonasal cancer, lymph node (LN) metastasis can affect prognosis and treatment. Hence, despite uncertain cost effectiveness, staging often includes regional LN cytology. This retrospective study evaluates how well physical examination and computed tomography (CT) perform as surrogates for regional LN cytology in dogs with sinonasal carcinomas and sarcomas. Dogs were included if their staging included physical examination, CT, and cytology of at least one regional LN. Physical examination parameters and tomographic appearance of the LNs were compared with cytologic descriptions to enable calculation of sensitivity and specificity, plus positive and negative predictive values (PPV and NPV). A total of 150 dogs were included. Fourteen dogs had cytologically confirmed LN metastasis; all 14 had carcinomas. Metastases were detected ipsilaterally in 12 dogs and bilaterally in two dogs. The sensitivity, specificity, PPV, and NPV of LN palpation alone were 71.4, 64, 17, and 96%, respectively; for CT alone, these were 100, 46.3, 16.1, and 100%; and for the combination of palpation and CT, these were 100, 59.5, 23.8, and 100%. Based on these results, detection of a palpably and tomographically normal LN in a dog with sinonasal carcinoma or sarcoma appears sufficient to confidently rule out cytologically detectable metastasis.