Small Animal Surgery Resident Oregon State University Albany, Oregon
Comparison of Canine Mast Cell Tumor Sentinel Lymph Node Mapping and Intraoperative Histocytologic Diagnostic Techniques for Lymph Node Metastasis. Alvarez-Sanchez A, Townsend KL, Milovancev M, Newsom L, Gorman E, Russell D. Oregon State University, Corvallis, OR.
Gold standards for canine mast cell tumor (MCT) sentinel lymph node (SLN) mapping and intraoperative metastasis detection are not established. The objective was to compare the SLN identification agreement of indirect computed tomographic lymphangiography (ICTL) and intraoperative near-infrared fluorescence (NIRF), and the accuracy of fine-needle aspirate (FNA) and imprint cytology (IC) at detecting metastases. Dogs with integumentary MCT were enrolled. The SLN identified on ICTL and/or NIRF, anatomic lymph node (ALN), and primary MCT were excised after NIRF. Fine-needle aspirates and IC were performed after LN excision. Agreement depended on the SLN matching the ALN or other LN. Accuracy of cytologic techniques was compared with histopathology. Twenty-four dogs underwent ICTL; 20/24 also underwent NIRF-surgery. No agreement between SLN and ALN occurred in 9/24 ICTL cases and 5/20 NIRF cases. Both techniques identified the same SLN in 19/20 cases. Thirty-five LN were removed. Metastases were detected on LN histology, FNA, and IC in 25/35 (19/20 dogs), 16/35 (12/20 dogs), and 15/35 (12/20 dogs), respectively. Fine-needle aspirates and IC were accurate in detecting LN metastases compared with histopathology in 24/35 and 21/35 LN. Both imaging techniques compared similarly when detecting SLN. Metastatic LN were detected in most dogs, and both intraoperative cytologic techniques proved less able to detect metastasis, despite direct sampling of excised LN compared with percutaneous FNA. The same SLN was detected in most cases irrespective of imaging technique. Our metastatic LN rate highlights the importance of accurate SLN detection and canine MCT may have a higher-than-expected metastatic LN rate.