Use of indirect computed tomography lymphangiography to determine metastatic status of sentinel lymph nodes in dogs with a pre‐operative diagnosis of melanoma or mast cell tumour

Abstract

Canine melanomas and mast cell tumours (MCTs) frequently metastasize to lymph nodes, worsening prognosis compared with dogs without metastasis. Sentinel lymph node (SLN) evaluation is more specific than evaluation of the lymph node closest to the tumour, which may not be the draining lymph node. Computed tomography lymphangiography (CTL) allows for SLN identification and one study of canine mammary tumours found that CTL was able to assist in determination of the metastatic status of inguinal SLNs prior to extirpation and histopathology. The objective of the present study was to evaluate CTL for use in determining metastasis to the SLN in dogs with a pre-operative diagnosis of melanoma or MCT in various locations by correlating CTL findings with histopathology. The hypothesis was that CTL would not be able to determine the metastatic status of lymph nodes, based on author experience. Dogs were prospectively enrolled and underwent CTL and subsequent SLN extirpation. Histopathology results for the primary tumour, SLN, and additional extirpated lymph nodes were recorded. Fifteen dogs were enrolled and 21 SLN were evaluated. The SLN enhancement pattern (heterogeneous, homogenous or peripheral) was not associated with metastasis, nor was the attenuation value at 1 minute, 5 minutes, or the change in attenuation value. No correlation was found between CTL findings and metastatic status of SLNs. Based on these results, CTL alone cannot be used to diagnose SLN metastasis. Extirpation of the SLN with histopathology is recommended to diagnose lymph node metastasis in dogs with melanoma and MCT.

Evaluating the Feasibility and Efficacy of a Dual-Modality Nanoparticle Contrast Agent (Nanotrast-CF800) for Image-Guided Sentinel Lymph Node Mapping in the Oral Cavity of Healthy Dogs

“…The majority of dogs (5/6) had detection of contrast-enhanced SLNs based on CT within 1–10 min following local injection within the oral cavity, which is slightly prolonged compared to previously reported studies. Canine studies investigating indirect CTL using water soluble iodinated contrast identified SLNs within 1–3 min following local injection despite variations in contrast volume and injection technique ( 6 , 28 , 29 ). The difference reported in our study could be associated with the liposomal nature of the novel contrast agent affecting transit time or other factors that may have affected lymphatic flow.…”

“…Patient positioning has been reported to be a factor that could affect lymphatic flow of tracer agents ( 15 , 34 ). Additional factors, such as endotracheal tube tie placement, can potentially impede lymphatic flow ( 29 ). Townsend et al evaluated the feasibility of ICG injected within the oral cavity of healthy dogs ( 25 ).…”

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

“…Another problem of utmost importance concerning prophylactic lymphadenectomy indication is related to the diagnostic methods to classify a dog as node-positive or negative. The clinical examination, upon which the WHO classification is based, is far from being accurate, as palpation as well as imaging studies are unreliable predictors of nodal metastasis by themselves [ 13 , 14 ].…”

Evaluating the feasibility and efficacy of a dual-modality nanoparticle contrast agent (Nanotrast-CF800) for image-guided sentinel lymph node mapping in the oral cavity of healthy dogs

“…Canine studies investigating indirect CTL using water soluble iodinated contrast identified SLNs within 1-3 minutes following local injection despite variations in contrast volume and injection technique. [28][29][30] The minor difference reported in our study could be associated with the liposomal nature of the novel contrast agent affecting transit time. In one case, the SLNs could not be identified until the 1 day p.i.…”