The Role of Interval Nodes in Sentinel Lymph Node Mapping and Dissection for Melanoma Patients

Abstract

In sentinel node (SN) biopsy, an interval SN is defined as a lymph node or group of lymph nodes located between the primary melanoma and an anatomically well-defined lymph node group directly draining the skin. As shown in previous reports, these interval SNs seem to be at the same metastatic risk as are SNs in the usual, classic areas. This study aimed to review the incidence, lymphatic anatomy, and metastatic risk of interval SNs. Methods: SN biopsy was performed at a tertiary center by a single surgical team on a cohort of 402 consecutive patients with primary melanoma. The triple technique of localization was used-that is, lymphoscintigraphy, blue dye, and g-probe. Otolaryngologic melanoma and mucosal melanoma were excluded from this analysis. SNs were examined by serial sectioning and immunohistochemistry. All patients with metastatic SNs were recommended to undergo a radical selective lymph node dissection. Results: The primary locations of the melanomas included the trunk (188), an upper limb (67), or a lower limb (147). Overall, 97 (24.1%) of the 402 SNs were metastatic. Interval SNs were observed in 18 patients, in all but 2 of whom classic SNs were also found. The location of the primary was truncal in 11 (61%) of the 18, upper limb in 5, and lower limb in 2. One patient with a dorsal melanoma had drainage exclusively in a cervicoscapular area that was shown on removal to contain not lymph node tissue but only a blue lymph channel without tumor cells. Apart from the interval SN, 13 patients had 1 classic SN area and 3 patients 2 classic SN areas. Of the 18 patients, 2 had at least 1 metastatic interval SN and 2 had a classic SN that was metastatic; overall, 4 (22.2%) of 18 patients were node-positive. Conclusion: We found that 2 of 18 interval SNs were metastatic: This study showed that preoperative lymphoscintigraphy must review all known lymphatic areas in order to exclude an interval SN.

EANM practice guidelines for lymphoscintigraphy and sentinel lymph node biopsy in melanoma

“…Early images help to discriminate true SLNs from the second-echelon nodes that are often observed. In melanomas of the trunk, usually bilateral static images of the axilla, trunk and groin are necessary [84,85]. Alternatively, body scanning from the neck to the groin can be performed.…”

Axillary Sentinel Lymph Node Biopsy for Breast Cancer and Melanoma Patients after Previous Axillary Surgery: A Systematic Review

“…This was already described in Sappey's drawings [33]. There are some connexions between superficial and deep lymphatic network [33], these may also account for interval sentinel nodes [38]. Of note, opening of lymphatic connections between deep and superficial network may prevent lymphedema after complete axillary dissection [39].…”

“…There is often more than one first-tier node [37]. Lymphatic drainage of the upper limb may rarely bypass level I and II of the axilla by using the way through lymphatics along cephalic vein and may drain directly in level III (infraclavicular fossa) [38]. This was already described in Sappey's drawings [33].…”

Interval sentinel lymph nodes in melanoma: a digital pathology analysis of Ki67 expression and microvascular density

“…The lymph nodes lie along the course of lymphatic collecting vessels between a primary tumor site and a draining node field are called interval nodes (INs) [4][5][6][7][8][9][10]. The frequency of INs is reported from 3 to 9.8 % [4][5][6][7][8][9][10][11][12][13][14][15][16]. This difference in prevalence is related to the quality of lymphoscintigraphy and to the different criteria used to classify a SLN as interval.…”