Nodal lymphatic mapping in 22 dogs bearing solid malignant tumors and enlarged regional lymph nodes: A descriptive study (2022–2025)

No data are available about the sentinel lymph node (SLN) mapping in presence of enlarged regional lymph nodes (eRLN), due to metastatic or inflammatory processes. The present study aims to assess the influence of eRLN clinically suspicious for nodal metastasis in SLN mapping in canine malignancies and describe possible alterations of the nodal lymphatic drainage and tracer uptake. Dogs with malignancies and eRLN were included and underwent to SLN mapping with lymphoscintigraphy and/or near-infrared fluorescence (NIRF). Findings in SLN mapping, distribution of nodal tracer uptake and histological nodal status were recorded. Twenty-two dogs with eRLN were included. During the lymphographies 2 patterns of nodal tracer distribution were observed: in 9 lymphographies (41%) only the eRLN (single or multiple) was identified (Pattern 1); in 13 (59%), beside the eRLN, at least one non-palpable/normal-sized SLN was identified (Pattern 2). The adjunctive SLNs were detected in the same (25%) or in a different (75%) lymphocentrum of the eRLN. The 54% of the adjunctive non-palpable/normal-sized SLN were metastatic. Among the pattern 2, in 3 lymphographies the eRLN had incomplete or absent nodal distribution of tracer uptake and the tracers were rerouted to one or more non-palpable/normal-sized SLN becoming the neo-SLN. Neoplastic or inflammatory status of the lymph node may alter the lymphatic drainage in example leading to find non-palpable/normal-sized SLN and various distribution of tracers' uptakes were recorded in eRLN. In presence of eRLN the SLN mapping is strongly suggested rather than limiting lymphadenectomy of only enlarged node, to avoid missing potentially residual microscopic neoplastic nodal disease in additional SLN.