Abstract
Sentinel lymph node (SLN) mapping is the current gold standard for the oncological staging of solid malignancies in humans. This prospective observational study describes the feasibility and the limits of preoperative lymphoscintigraphy for SLN detection in dogs with spontaneous malignancies and the improvements in staging accuracy. Client‐owned dogs with confirmed malignant neoplasia and absence of distant metastasis were prospectively enrolled. Lymphoscintigraphy was performed after the peritumoral injection of Technetium‐99m labeled nanocolloids. Regional dynamic and static images were acquired, with and without masking of the injection site with a lead shield. The dogs were then subjected to surgery for tumor excision and SLN extirpation. Intraoperative SLN detection was performed by combining methylene blue dye and a dedicated gamma probe. Overall, 51 dogs with a total of 60 solid malignant tumors were enrolled. Lymphoscintigraphy identified at least one SLN in 57 of 60 cases (95%). The SLN did not always correspond to the regional lymph node (35/57, 61.4%). The use of a lead shield, masking the injection site, markedly improved the SLN visibility. The median time of SLN appearance was 11.4 ± 9.3 min. No side effects were observed. Preoperative lymphoscintigraphy allows for SLN detection in dogs and can improve staging accuracy by either identifying the SLN in a different lymphosome than clinically expected or discriminating the draining node in uncertain cases. The combined use of preoperative and intraoperative techniques is recommended to increase the SLN detection rate.
Highlights
The sentinel lymph node (SLN) is the first lymph node (LN) that receives direct lymphatic drainage from a primary tumor site.[1]
Tumor-induced lymphangiogenesis increases the variability of lymphatic drainage patterns, hampering the possibility of SLN identification based on anatomical location alone.[5]
The present study aimed to describe the feasibility and effectiveness of preoperative lymphoscintigraphy for SLN detection in canine patients with spontaneous malignancies in different anatomical locations
Summary
The sentinel lymph node (SLN) is the first lymph node (LN) that receives direct lymphatic drainage from a primary tumor site.[1] In veterinary medicine, sampling the regional lymph nodes (RLN), only when palpably enlarged, is notoriously inaccurate, whereas sampling an inappropriate LN might lead to false-negative results and thereby understaging.[2,3,4] Tumor-induced lymphangiogenesis increases the variability of lymphatic drainage patterns, hampering the possibility of SLN identification based on anatomical location alone.[5] SLN mapping procedure indicates the correct LN to be assessed for the presence of nodal metastasis, allowing a more accurate tumor staging, aiding treatment decision and prognostication.[6,7,8,9] a potential therapeutic role of early nodal intervention in oncological patients with no signs of lymphadenopathy has been hypothesized, it remains to be investigated in both, human[10] and canine[11] oncology. Radiocolloids for SLN mapping includes preoperative planar lymphoscintigraphy as well as intraoperative nodal detection with a hand-held gamma probe. Tracers with smaller particle sizes ensure visualization of a greater number of LNs, they lead to difficulties in image interpretation and intraoperative SLN identification.[12]
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