Reconfirmation of Clinical Unpredictability of Lymphatic Drainage in Cutaneous Melanoma and New Developments in Sentinel Lymph Node Diagnostics

TO THE EDITOR: I read with interest the continuing education article by Uren et al. (1) stating that clinical prediction of lymphatic drainage from the skin is not possible and that the old clinical guidelines based on Sappey’s lines therefore should be abandoned. To the best of my knowledge, my former group at the Hospital of the Frankfurt Goethe University was the first ever to standardize scintigraphic mapping of lymphatic drainage in cutaneous tumors, particularly malignant melanoma, in the late 1970s and early 1980s (2–4). We were able to clearly document that not only tumors located inside but also outside lymphatic watersheds of the skin show an ambiguous lymphatic drainage, which is practically unpredictable by conventional anatomic guidelines in individual patients. We concluded that the anatomic thesis of lymphatic watersheds should be revised. In more than 90% of our patients with skin lesions on the trunk, one or both axillary lymph node groups were found to be involved in lymphatic drainage, either solely or combined with inguinal, supraclavicular, posterior cervical, parasternal, or other node-bearing areas or in-transit lymph nodes; hence, the axillary lymph node groups as the “center in lymphatic drainage from the truncal skin in man” should attract our greatest attention in melanomas or other cutaneous tumors of the trunk independent of their topographic position (3). Our data on the lymphatic drainage patterns in skin tumors of trunk, head and neck, and upper and lower limbs published some 20 y ago were proven to be true (1,5). Detection and localization of “true” sentinel lymph nodes, permitting correct staging of regional lymph nodes, is essential for management and prognostic assessment in malignant melanoma. In 43 of the 100 melanoma patients examined prospectively, additional information was obtained by simple temporary lead shielding of hot spots in lymphatic drainage areas, applied in combination with dynamic acquisition in various views: In 7 patients, the exact course of lymph vessels could be mapped only after shielding; in 3 patients, hot spots in the drainage area proved to be lymph vessels, lymph vessel intersections, or lymph vessel ectasias; in 33 patients, 1 or 2 additional sentinel lymph nodes that showed less tracer accumulation or were smaller ( 1.5 cm) were detected after shielding by visualization of their own lymph vessels (7% sentinel lymph node metastases) (6). Preliminary data from another prospective study on 276 melanoma patients indicated that the time of scintigraphic appearance of sentinel lymph nodes is a clinically relevant factor for prediction of metastatic spread to sentinel lymph nodes, provided the time of appearance is assessed under standardized conditions (7). However, larger numbers of patients need to be examined to truly evaluate the benefit of the time of scintigraphic appearance compared with other predictors of sentinel lymph node tumor positivity. Finally, we have created a classification of the lymphatic drainage status of primary tumors that preferably metastasize via their draining lymph vessels (8). The classification is based on the number of sentinel lymph nodes and their locations (node group or in-transit node) and comprises 4 classes (D-class I–IV) and distinct subclasses (A–E): For example, D-IA means 1 draining node location (NL) and 1 sentinel lymph node (SN); D-IIA means 2 NL, 2 1 SN; D-IIIB means 3 NL, 1 1 SN; and D-IVE means 4 NL, 4 1 SN. The classification is easy to learn and reliably reproducible using various approaches (e.g., -camera imaging, -probe detection, or dye mapping). We are currently testing its diagnostic, prognostic, and therapeutic value in prospective studies on melanoma and breast cancer patients and encourage others to join us.