Influence of locoregional lymph node aspiration cytology vs sentinel lymph node mapping and biopsy on disease stage assignment in dogs with integumentary mast cell tumors

• Published in: Veterinary surgery Vol. 50; no. 1; pp. 133 - 141
• Main Authors: Lapsley, Janis, Hayes, Galina M., Janvier, Valentin, Newman, Ashleigh W., Peters‐Kennedy, Jeanine, Balkman, Cheryl, Sumner, Julia P., Johnson, Philippa
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.01.2021; Blackwell Publishing Ltd
• Subjects: Animals; Biopsy; Biopsy, Fine-Needle - veterinary; Cellular biology; Computation; Computed tomography; Cytological Techniques - veterinary; Cytology; Diagnostic systems; Dogs; excision; experimental design; Female; Health services; Histological Techniques - veterinary; Histology; histopathology; hospitals; Injection; lymph; Lymph nodes; Lymphangiography; Lymphatic system; Male; mast cells; Mast Cells - pathology; Metastases; metastasis; Neoplasm Staging - veterinary; Sentinel Lymph Node - cytology; Sentinel Lymph Node - pathology; Sentinel Lymph Node Biopsy - veterinary; Tumors
• ISSN: 0161-3499; 1532-950X; 1532-950X
• DOI: 10.1111/vsu.13537

Objective To compare the effect of sentinel lymph node (SLN) histology vs locoregional lymph node (LRLN) fine needle aspiration (FNA) cytology on assigned disease stage and adjunctive treatment recommendations and describe the incidence of anatomic disparity between the LRLN and SLN. Study design A pre‐post study refers to a study design type in which subjects are compared pre and post the intervention of interest. Animals Seventeen dogs undergoing primary excision of 20 cutaneous and subcutaneous mast cell tumors (MCT). Methods Client‐owned dogs presenting to the Cornell University Hospital for Animals for surgical removal of a cytologically confirmed cutaneous or subcutaneous MCT >1 cm in diameter were enrolled. Cytological examination of FNA from the LRLN was compared with histology of the SLN. The SLN was identified by indirect computed tomographic lymphangiography (ICTL) after peritumoral injection of iopamidol and scanning at 1, 3, 5, 10, and 15 minutes. Histopathologic node score > 1 was considered metastatic. After case review by an oncologist, LRLN FNA cytology was compared with SLN histology for effect on changes in stage assignment and adjunctive treatment recommendations. Results Mast cell tumors were graded as 2 low (n = 11), 2 high (n = 2), and subcutaneous (n = 7). Optimal scan timing was 10 minutes after injection of iopamidol. Sentinel lymph node differed anatomically from LRLN in 5 of 18 scans. Metastases were detected by histology in 9 of 20 SLN compared with in 1 of 20 FNA of LRLN (P = .001), changing stage and adjunctive treatment recommendations 8 of 20 tumors. Only 6 of 19 LRLN FNA samples were diagnostic. Conclusion Sentinel lymph nodes were consistently identified with ICTL and differed from LRLN in one‐quarter of tumors. Histopathological examination of SLN altered recommendations in half of the dogs compared with the previous standard of care. Clinical significance Indirect computed tomographic lymphangiography and SLN excision should be considered as a new standard for dogs with MCT.