Sentinel Lymph Node Radiolocalization in Head and Neck Squamous Carcinoma: Curious Methods

For head and neck squamous cell carcinoma, as well as for most solid tumors, the presence of lymph node metastasis is the most important prognostic factor. The morbidity, and possibly the lack of therapeutic benefit, of elective lymph node dissection in N0 patients for breast cancer and melanoma have made minimally invasive approaches attractive. In this context, the sentinel node (SLN) concept was formulated, first by Cabanas for penile squamous cell and later by Morton for melanoma and Giuliano for breast carcinoma. The SLN concept supposes that the oncologic status of one or few lymph nodes can predict the presence of metastatic disease in the remaining lymph nodes of the draining basin. The strongest point in the SLN concept is that a negative SLN biopsy should predict the absence of metastatic cells in the entire regional lymph basin. The SLN concept can be considered validated for breast carcinoma, and although it has been accepted as the standard of care for melanoma, it has not been formally validated. The sentinel node concept is a hypothesis and as such has to be validated or proven before it can be applied for every type of cancer histology and location. Early studies in head and neck squamous cell carcinoma were not very successful in identifying the SLN, probably because of inadequate timing of injection and dissection and the difficulty of separating the gamma signal of the primary from that of the SLN. In a recent study, Alex et al. have reported a 100% SLN detection rate and no false-positives in eight patients. Technetium sulfur colloid was used as the sole tracer and the detection was performed with a handheld gamma probe, without preoperative lymphoscintigraphy. Although these results are encouraging and should incite others to pursue the technique, several points need clarification: