Sentinel Lymph Node Mapping and Biopsy in Cats with Solid Malignancies: An Explorative Study

SIMPLE SUMMARY: The sentinel lymph node (SLN) is the first node in the basin that drains a solid tumor, and its histopathological examination after surgical removal is recommended in dogs and humans for correct tumor staging. In cats, however, the implementation of SLN biopsy (SLNB) has never been described. In this study, we included 12 cats presented with 14 solid malignancies that underwent surgical excision of a solid tumor and SLNB. The mapping technique used, location and number of SLN, correspondence with the regional lymph node (RLN), and histological status of the SLN were determined. The detection rate and complications of SLNB were also recorded. Near-infrared fluorescence lymphography (NIRF-L) was performed in 64.3% of tumors and lymphoscintigraphy in 35.7%. The detection rate was 100% for both techniques. The SLN did not correspond (fully or partially) to the RLN in 71.4% of cases, with multiple SLN being excised in 9/14 tumors. No complications related to SLNB were recorded. At histopathology, metastases were identified in 41.7% of cats, all with MCT. SLNB guided by NIRF-L or lymphoscintigraphy seems to be feasible and safe in cats with solid tumors and should be suggested for correct tumor staging in cats, especially with MCT. ABSTRACT: There is increasing evidence on the utility of sentinel lymph node (SLN) biopsy (SLNB) for the staging of dogs with various malignancies; however, comparable information is missing in cats. This multi-institutional study aims at reporting the feasibility and detection rate of SLNB guided by lymphoscintigraphy and the blue dye or near-infrared fluorescent lymphography (NIRF-L) in cats with solid tumors. In total, 12 cats presented with 14 solid malignancies that underwent curative-intent surgical excision of the primary tumor and SLNB were retrospectively enrolled. The mapping technique used, location and number of SLN, correspondence with the regional lymph node (RLN), and histological status of the SLN were retrieved. The detection rate and complications of SLNB were also recorded. NIRF-L was performed in 64.3% of tumors and lymphoscintigraphy in 35.7%. The detection rate was 100% for both techniques. The SLN did not correspond (fully or partially) to the RLN in 71.4% of cases, with multiple SLN being excised in 9/14 tumors. No complications related to SLNB were recorded. At histopathology, metastases were identified in 41.7% of cats, all with mast cell tumors (MCT). SLNB guided by NIRF-L or lymphoscintigraphy is feasible and safe in cats with solid tumors and should be suggested for correct tumor staging in cats, especially with MCT.