A cadaveric study of auricular lymphatics and implications for sentinel lymph node biopsy

Malignant cutaneous tumors of the auricle are known to have a high rate of spread to the regional lymph nodes, and, for this reason, removal of the lymph nodes, for diagnostic or therapeutic purposes, is often required. Recent experience with sentinel node biopsy in cutaneous tumors of the head and neck has questioned the traditional lymphatic pathways and prompted a new study. Lymphatic pathways from the auricle were demonstrated by India ink injection of five auricles in three cadavers followed by block dissection and Spalteholz clearing of en bloc specimens. Lymphatics descend adjacent to the mastoid bone periosteum and lie deep to the insertion of the sternocleidomastoid muscle. There are five different locations for sentinel nodes: superficial parotid, anterior mastoid, infra-auricular parotid, deep to sternocleidomastoid, and lateral mastoid. Two of these nodal locations (anterior and lateral mastoid) may be bypassed by anastomotic pathways. We conclude that, first, echelon lymph nodes lie in five different sites, some bypassed by anastomotic lymphatics. Lymphatics from the ear lie close to the mastoid bone and pass deep to the insertion of sternocleidomastoid where they may be difficult to follow. Sentinel lymph node biopsy for cutaneous tumors of the auricle is possible, but the presence of skip metastases should be considered.