Lymphatic Mapping and Sentinel Node Biopsy: A Surgical Perspective Ronald N. Kaleya, MD, FACS,* Jason T. Heckman, MD,* Michael Most, MD, † and Jonathan S. Zager, MD,* Lymphatic mapping and sentinel node biopsy has been rapidly and widely adopted by the surgical community as an oncologic equivalent elective lymphadenectomy for regional node staging in both melanoma and breast cancer. Despite being the de facto standard of care, it remains a highly unstandardized procedure surrounded by many unresolved con- troversies for surgeons who perform the procedure. The controversies are as basic as the definition of the real sentinel node and as specific as the appropriate localization pharma- ceutical(s), site of injection, timing of the injection, and utility of external scintigraphy (dynamic versus. static). Furthermore, questions regarding surgical training, indications, and contraindications remain unanswered. Because there are few long-term studies strat- ified by technique and indication, the resolution of these surgical controversies are unlikely in the near future. Semin Nucl Med 35:129-134 © 2005 Elsevier Inc. All rights reserved. A s surgical procedures have become increasing less inva- sive techniques during the past 2 decades, the treatment of the regional lymph nodes has followed this trend. As a result, intraoperative lymphatic mapping (IOLM) and senti- nel node biopsy (SLNB) has been rapidly and widely adopted as on oncologic equivalent to elective lymph node dissection. Predicated on the assumption that solid tumors spread in an orderly progression to the regional nodes before systemic dissemination, lymphadenectomy has been used in the cur- ative therapy for breast cancer, colon cancer, melanoma, and gynecologic malignancies, among others. This assumption, however, has not been validated for any cancer in random- ized, controlled trials comparing the efficacy of routine lymphadenectomy to observation. Hematogenous spread may precede or be coincident with lymphatic spread for many solid tumors. Failing to show a survival benefit for regional lymphadenectomy, the current justifications for nodal evaluation are staging, determination of the need for additional therapy and loco-regional control of the tumor. Because at least 80% of node dissections in breast cancer and melanoma fail to show occult disease, the benefit of lymph- adenectomy, when compared with morbidity and costs, may not be warranted. Sentinel node biopsy provides the same information, converts elective or prophylactic node dissec- tions into directed therapeutic node dissections, and confines the morbidity of the procedure to those patients who could potentially benefit from removal of involved lymph nodes. Not only does the definition of what constitutes the real sentinel node vary from study to study, but the protocols used for localization and harvesting of the sentinel node dif- fer between institutions, making comparison of results diffi- cult. IOLM and SLNB has, therefore, become an unstandard- ized standard of care. Thus, from the surgeon’s viewpoint, the critical issues and controversies surrounding IOLM and SLNB include the following (Table 1): validation as an onco- logically equivalent to elective lymphadenectomy, site of in- jection for the mapping procedure, appropriate localizing pharmaceutical(s), timing of the injection, the utility of ex- ternal scintigraphy (dynamic versus. static), and value of IOLM and SLNB in several specialized situation (ie, large tumors or following neoadjuvant chemotherapy). The Sentinel Node: A Precise Definition The sentinel node is the first draining lymph node on the direct drainage pathway from the primary tumor site. 1 How- ever, there are several surrogate definitions depending on the mapping technique used to localize the SLN. Clinical defini- tions include (1) nodes that stain blue and have a blue- stained afferent lymphatic, (2) a blue-stained node, (3) a *Department of Surgery, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY. †Department of Surgery, Beth Israel Medical Center, New York, NY. Address reprint requests to Ronald Kaleya, MD, 440 East 79th Street, New York, NY 10021. E-mail: rkaleya@chpnet.org 129 0001-2998/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.semnuclmed.2004.11.004