Clinical applications of sentinel lymph-node biopsy for the staging and treatment of solid neoplasms

A review of the clinical applications of sentinel lymph node (sN) biopsy has been performed with the aim of defining the rationale, the methods of detection, the accuracy, and the current indications to sN biopsy in different solid neoplasms. In melanoma patients, sN biopsy represents a standard procedure for staging purpose, although its therapeutic value is still under examination. The sN is an accurate method for the pathologic staging of the axilla in patients with early stage breast cancer, and it can be useful for the selection of patients with axillary metastasis who should undergo standard axillary dissection. In gynecologic malignancies, appreciable results are available in patients with vulvar and cervical cancer only. Patients with squamous cell vulvar cancer may benefit by sN biopsy because a complete bilateral inguino-femoral lymph-node dissection may be avoided whenever the sN is free of metastasis. As regards to cervical cancer, further studies are required with the combined technique (blue dye injection and gamma-probe guided surgery), which seems more promising, before abandoning pelvic lymphadenectomy in patients with histologically-negative sN. The experience in urologic cancer deals mainly with penile and prostate cancer; the modern procedures for the dynamic detection of sN are going to clarify its role in the surgical management of penile cancer; as regards to prostate cancer, very preliminary results suggest that the sN biopsy may enhance the pathologic staging of this neoplasm compared to modified pelvic lymphadenectomy, due to the individual variability of the lymphatic drainage of this cancer. In patients with clinically node-negative squamous head and neck cancer, the reliability of sN-guided neck lymph node dissection seems promising. The sN biopsy is also technically feasible in patients with differentiated thyroid cancer; however, the future role of this procedure in the clinical decision-making of these patients remains to be defined due to the questionable biological meaning of nodal metastases. Patients with non-small-cell lung cancer should be investigated by means of radiotracers injected at the time of thoracotomy or under CT-scan guidance in order to achieve a satisfactory identification rate (over 80%); the focused histopathologic staging of the sN improves current pathologic staging by conventional bi-valve assessment of all the lymph nodes of the surgical specimen; moreover, the prognostic role of isolated N2 metastasis can be better elucidated. In patients with gastrointestinal malignancies, the intraoperative lymphatic mapping with sN biopsy have suggested that the lymphatic drainage of the gastrointestinal tract is much more complicated than other sites, skip metastasis being rather frequent. In patients with gastric cancer, current data show that it can be detected by means of peritumoral injection of indocyanine green; the detection of tumor positive lymph nodes beyond the perigastric area could select patients amenable to D2 lymphadenectomy. As regards to colorectal cancer patients, the focused analysis of the sN may reveal disease that might otherwise go undetected by conventional surgical and pathological methods, and those patients which are upstaged can benefit by adjuvant chemotherapy. Finally, in patients with Merkel cell carcinoma, notwithstanding the limited experiences with sN biopsy, sN histology seems to predict regional lymph node status and may aid in selecting which patients are amenable to therapeutic lymph node dissection.