Biopsy of sentinel lymph nodes after injection of methylene blue and lymphoscintigraphic guidance in 30 dogs with mast cell tumors

Abstract

Objective -To report the outcomes associated with sentinel lymph nodes (SLNs) detection and extirpation guided by radionuclide and methylene blue injections in dogs with cutaneous and subcutaneous mast cell tumors (MCTs).Study Design -Clinical prospective cohort study. Animals -30 client-owned dogs with MCTs amenable to wide-margin excision, without evidence of distant metastasis and abnormal regional lymph nodes (RLNs).Methods -Technetium-99m and methylene blue were injected peritumorally. Dogs underwent pre-operative gamma camera scintigraphy, and an intraoperative gamma probe guided SLN extirpation. Outcomes included technical and surgical complications, number of SLNs, SLNs location respecting the expected RLN, and histopathology results.Results -SLN mapping was applied to 34 MCTs in 30 dogs without any complication.SLNs were not identified in 3/34 tumors, all with previous scar tissue. SLNs did not correspond to expected RLNs in 19/30 (63%) tumors. Histological examination confirmed an early or overt metastasis in 32/57 (56%) SLNs extirpated.Conclusion -SLN mapping and biopsy with radionuclide and injection of methylene blue was associated with low morbidity and allowed detection of SLNs in dogs with MCT at first presentation without scar tissue.Clinical significance -Incorporation of SLN mapping and extirpation allows for a personalized staging approach in dogs with MCT. The presence of scar tissue in dogs with recurrent tumors seems to be a limitation for SLN mapping with this technique.

Contrast‐enhanced ultrasound for sentinel lymph node mapping in the routine staging of canine mast cell tumours: A feasibility study

“…MCTs was 60%, which is similar to what was previously reported using regional lymphoscintigraphy combined with intra-operative lymphoscintigraphy and blue dye. 15,16 It is however higher than the 42% previously reported in our institution when SLN mapping was not part of the routine staging, 12 and the 45.9% reported in another study. 13 This supports the effectiveness of CEUS SLN mapping; but unlike in these two retrospective studies, in this current study all histological sections were stained with toluidine blue, which may also have affected these results.…”

“…Afferent lymphatic tracts were easily identified from the injection sites but were difficult to follow all the way to the SLN(s). lymphoscintigraphy/intraoperative methylene blue techniques, 15,16 respectively. In humans, lymphosonography also identifies at least one SLN in 89% to 97% of patients, which is not different from the traditional techniques.…”

“…30,[32][33][34] An average of 1.2 (74/62) SLNs per MCT was identified using CEUS, whereas an average of 1.6 (88/54) SLNs per MCT was identified with lymphoscintigraphy/ intraoperative methylene blue, when compiling the cases from two studies. 15,16 It is difficult to compare these figures, but it is possible that the dual-labelled technique truly identifies a higher number of LNs. Indeed, radiopharmaceuticals and blue dyes are associated with significant spill-over resulting in the identification of nonsentinel LNs.…”

“…14 Regional lymphoscintigraphy combined with intra-operative lymphoscintigraphy and blue dye, the gold standard SLN mapping technique in human oncology, has been successfully incorporated into canine MCT staging in previous studies. 15,16 Lymphoscintigraphy is however, only available in very few veterinary centres. The use of computed-tomography (CT) SLN mapping is mainly restricted to Japan in human oncology, 17 but is becoming a very popular technique among veterinarians.…”

A retrospective study on prophylactic regional lymphadenectomy versus nodal observation only in the management of dogs with stage I, completely resected, low-grade cutaneous mast cell tumors

“…Additionally, if the LNs are not palpable, they may not undergo cytological evaluation, so the nodal status is often unknown at the time of surgery. Because the therapeutic role of HN2 LN extirpation has been previously demonstrated, 4 and due to the lack of complications related to lymphadenectomy (which has been documented here and in previous studies) 7,8,21 , to recommend this additional surgical procedure may not be viewed as unnecessary or harmful. On the contrary, it may provide a clinical benefit, as shown by the reduced incidence of MCT progression found in the current series.…”