Use of 2% methylene blue dye for location of axillary lymph node in bitches (Canis familiaris – Linnaeus, 1758)

Abstract

A biopsy of sentinel lymph node (SLN) is increasingly used to determine tumor clinical staging. The involvement of lymph nodes in veterinary patients has strong prognostic value in mammary gland tumors. There is a lack of well established guidelines for the evaluation of the SLN in veterinary medicine. The purpose of this research was to evaluate the efficacy of 2% methylene blue dye in identifying axillary lymph node in dogs. Thus, we used 101 bitches suffering from breast lesions that underwent unilateral or bilateral mastectomy. Before surgery, sterile 2% methylene blue solution was applied intradermally in the area around the cranial thoracic gland. The dye was effective in identifying axillary lymph node in 76.27% of mammary chains. Blue stained structures similar to lymph nodes were obtained in 78.81% of cases and 96.77% of these structures were confirmed histopathologically as lymph nodes. Given the prognostic significance of lymph node involvement in some tumors, evaluation of SLN should be incorporated into clinical routine in order to allow a more accurate clinical staging of bitches with breast cancer.