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

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.

The Role of Sentinel Node Mapping and Lymphadenectomies in Veterinary Surgical Oncology

“…SLNs may be the regional LNs anticipated to be responsible for tumor drainage; however, the LNs at unpredictable anatomical locations might also serve as SLNs [20]. Indeed, for dogs, regional LNs do not correspond to SLNs in 42-63% of cases [10,20,24,25], and a recent study in cats found an even higher discrepancy (71.4%) [26].…”

“…The same group also published a study evaluating lymphoscintigraphy in head and neck tumors, for which a lower detection rate of 83% was observed [13]. Finally, a recent study revealed the successful usage of lymphoscintigraphy for the detection of SLN in cats with various solid tumors [26].…”

“…contrast-enhanced ultrasound (CEUS) [32], single-photon emission computed tomography (SPECT) [33], positron emission tomography (PET) [34], pre-and intraoperative lymphoscintigraphy, and the injection of blue dyes for direct visualization or fluorescent dyes for near-infrared (NIR) fluorescent imaging [35]. Corresponding evaluations of indirect radiographic [36][37][38] and CT lymphography [39][40][41][42], lymphoscintigraphy [15,20,24,[43][44][45][46][47], CEUS [25,48], methylene blue staining [20,24,47], and NIR-lymphography [14,47,[49][50][51] are also available for dogs and, most recently, also for cats [26,52].…”

“…The improved detection rate of metastatic disease was achieved by a combination of improved resection success and the identification of the SLNs different from the expected regional nodes [14]. A first case report showing the feasibility of SLN mapping in a cat also bearing a mast cell tumor has just been published, followed by a pilot study in cats with different solid neoplasms [26,52]. Finally, Gariboldi et al very recently published a study that proved that the SLN mapping of scars from previous tumor excision is also possible using lymphoscintigraphy or NIR lymphography [49].…”

Comparative aspects of targeted sentinel lymph node mapping in veterinary and human medicine: opportunities for future research

“…Indocyanine green also has an excellent safety profile and has been demonstrated to have no significant side effects in companion animals ( 49 ). Applications have included SLN mapping of the oral, head and neck region, caudal abdomen and limbs in healthy and diseased dogs and head and neck region, trunk, perineum, and limbs in healthy and diseased cats ( Figure 3 ) ( 22 , 29 , 41 , 46 , 47 , 50 ). As a result, this technique is gaining popularity in the veterinary field; however, limitations include the accessibility of NIRF equipment and a lack of protocol standardization.…”