Indocyanine-based near-infrared lymphography for real-time detection of lymphatics in a cat with multiple mast cell tumours

Abstract

Case summary An 11-year-old female domestic shorthair cat was presented with cutaneous mast cell tumours (MCTs) localised at the right temporal region, the left buccal region and on the third digit of the right thoracic limb. Staging was negative and locoregional lymph nodes appeared normal, based on clinical findings. During surgery, real-time indocyanine green (ICG)-based lymphography was performed to detect the cutaneous draining pattern of all the primary MCTs. ICG was injected intracutaneously in four quadrants around each tumour, and a clear lymphogram was visible shortly after injection. Using near-infrared lymphography (NIR-L) for guidance, all lymphadenectomies were performed in 12 mins or less, with a maximal incision length of 3.5 cm. The smallest resected node was 0.9 cm in diameter. All MCTs were classified as low-grade cutaneous MCT. All four ICG-positive lymph nodes were considered premetastatic or metastatic. The only ICG-negative resected node was also negative for tumour cells. No complications related to NIR-L were recorded. Relevance and novel information This is the first description of NIR-L in a cat with MCT. Application was straightforward and ICG enrichment only occurred in the metastatic nodes, suggesting correct identification of lymphatic draining patterns. Of note, as previously described in dogs, we did detect nodal metastasis, despite low-grade primary tumours. The clinical relevance should be evaluated in future studies.

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

“…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].…”

“…Lately, several metareviews in human medicine have confirmed NIR imaging using ICG as a reliable mapping technique compared with the gold standard lymphoscintigraphy [35,77]. After NIR SLN mapping in dogs was initially described in experimental studies in dogs and pigs [50], it is now gaining increased interest in veterinary surgical oncology [14,49,52]. Beer et al published a retrospective study on NIR lymphography in dogs with mast cell tumors.…”

“…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].…”

“…The improved visualization of small and nonpalpable nodes results in a significantly increased success rate of lymphadenectomies compared with unguided lymphadenectomies in dogs [14]. No mapping-related complications have been reported in dogs or cats [14,49,52,78,79]. The disadvantages of NIR include its low depth of penetration, limited to a few millimeters to centimeters, and that it does not allow the identification of sentinel nodes in body cavities without surgical access to allow visual inspection [72].…”

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

“…A tendency to lymphatic spread and nodal metastases is reported for various feline solid tumors [ 11 , 28 , 29 ]. In a recent study, metastases to the lymph nodes have been documented in 58.8% of cats with MCT, underscoring the importance of nodal assessment also in this species [ 30 ]. However, there is still considerable inconsistency among studies on indications and methods for nodal staging in cats, and most studies do not even include information on the status of the lymphatic basin [ 11 , 28 , 29 ].…”