An interview with Stefano Zanardi – the 2026 Melton Award winner

16 March 2026

The 2026 Melton Award for the best published paper in small animal surgery in the Journal of Small Animal Practice was awarded to Stefano Zanardi. We asked Stefano about his research assessing the use of methylene blue in sentinel lymph node identification in dogs with low-grade mast cell tumours, and what he learnt from the study.

How did you become involved in the study?

The rationale for this study stems from the need to identify an effective, low-cost method for sentinel lymph node detection in dogs. In our clinical practice, we manage a large number of mast cell tumour cases requiring lymphadenectomy, and in many instances, we have had to rely solely on regional lymph node removal, particularly when financial constraints limited access to advanced mapping techniques.

Therefore, we aimed to investigate a more accessible approach by evaluating the use of methylene blue, assessing both its effectiveness in sentinel lymph node identification and its utility in improving intraoperative lymph node visualization.

What question(s) did your research tackle?

Our research aimed to determine whether methylene blue could serve as an effective standalone technique for sentinel lymph node identification in dogs. We also evaluated the time required for lymph node uptake of the dye and whether its use might reduce the duration of the lymphadenectomy procedure. In addition, we assessed the safety profile of methylene blue by systematically recording any adverse effects associated with its administration.

Briefly, what were the main findings of your study?

We found that intraoperative peritumoral methylene blue injection was effective as a standalone mapping technique for sentinel lymph node identification in dogs with low-grade mast cell tumours. At least one stained lymph node was detected in 88% of cases. Importantly, all metastatic lymph nodes (HN2/HN3) were stained, while all unstained lymph nodes were histologically non-metastatic (HN0/HN1). No complications related to methylene blue injection were observed, supporting the safety of this technique. Although the dye subjectively improved intraoperative visualisation, no statistically significant differences in lymphadenectomy time were detected between stained and unstained lymph nodes.

Were the results what you expected, or were you surprised by the outcome?

The results were largely consistent with our expectations, as we hypothesised that methylene blue would reliably identify sentinel lymph nodes and that unstained nodes would most likely be non-metastatic. However, we were positively surprised by the strong correlation between staining and histologic metastatic status, particularly the finding that all non-metastatic lymph nodes were unstained. This observation further supports the potential reliability of methylene blue as a standalone mapping technique, especially in low-resource settings.

Considering that our study population included only dogs with low-grade mast cell tumours, the relatively high proportion of metastatic lymph nodes underscores the importance of performing lymphadenectomy in these patients to ensure accurate staging and appropriate treatment planning.

We were also somewhat surprised by the lack of a statistically significant difference in lymphadenectomy time between stained and unstained lymph nodes. This may be attributable to variability in anatomical locations and procedural complexity among the lymphadenectomies performed. Subjectively, the contrast provided by the blue dye did facilitate intraoperative lymph node identification, even though this did not translate into a measurable reduction in surgical time.

What is the key message you’d like veterinary professionals to take away from the study?

The key message is that methylene blue represents a reliable, low-cost technique for sentinel lymph node identification in dogs with low-grade mast cell tumours. Whenever possible, preoperative sentinel lymph node mapping should remain the standard of care in these patients. However, when preoperative mapping is not feasible for any reason, intraoperative methylene blue injection may serve as a valuable alternative with a favourable cost/benefit profile.

Read the paper “Intraoperative methylene blue staining is effective as a single mapping technique in the identification of sentinel lymph nodes in dogs with low-grade mast cell tumours” in JSAP here.