Sentinel Lymph Node Biopsy: What’s Ahead (and Neck) in Melanoma?
Abstract & Commentary
Synopsis: In this study, 30 patients with melanoma of the head and neck underwent a sentinel lymph node biopsy. Problems are encountered in this population due to unique aspects of the anatomy of the head and neck.
Source: Jansen L, et al. Head Neck 2000;22:27-33.
Sentinel lymph node biopsy in head and neck cancer can be complicated by unique anatomical difficulties. In the study by Jansen and colleagues, 30 patients with melanoma of the head and neck from two centers in The Netherlands underwent preoperative lymphoscintigraphy and sentinel lymphadectomy ("sentinel node biopsy") between 1994 and 1997. The lesions were required to be greater than 1 mm deep and the therapeutic wide local excision was done after the sentinel node biopsy. The median Breslow thickness was 3.0 mm with ulceration present in 30%. Locations included the face in six cases, the scalp in eight cases, the ear in four cases, and the neck in 12 cases.
The surgical technique, described in detail in the paper, included the use of preoperative lymphoscintigraphy with Tc-labeled human albumin and intraoperative location of the sentinel nodes using both a gamma probe and visual inspection for blue dye. The average number of sentinel nodes removed was 2.6 per patient, although in three cases no sentinel nodes were identified. Fifty-three percent of these nodes were both blue and radioactive, 43% were radioactive only, and 4% were blue only.
One problem unique to the head and neck is the presence of sentinel lymph nodes within the parotid gland. Four nodes within the parotid gland identified by preoperative lymphoscintigraphy in this study were not removed. However, of the 70 total lymph nodes excised, 13 came from the parotid gland. Another problem in the head and neck region is that not all sentinel lymph nodes can be seen preoperatively due to their anatomical proximity to either the injected site or another sentinel node. This difficulty helps explain 18 harvested sentinel nodes that were not identified on lymphoscintigraphy because of their location relative to the primary tumor (2 nodes) or other nodes (16 nodes).
Sentinel nodes were processed with six permanent histologic sections (12 if the node was larger than 1 cm) and stained with H&E, S100, and HMB45. This led to eight of these high-risk patients having a positive result. A formal lymph node dissection was performed in six patients. It is not reported if any patients received postoperative adjuvant therapy. Nevertheless, with an average follow-up of nearly two years, five of eight patients (62.5%) with a positive sentinel node were disease-free compared with 15 of 19 patients (78.9%) with a negative sentinel node.
COMMENT by Kenneth W. Kotz, MD
While it is clear that preoperative lymphoscintigraphy with sentinel lymphadenectomy is feasible and can provide prognostic information, has it been proven to provide a therapeutic advantage? Also, at what Breslow’s depth is the probability of finding a positive sentinel node likely enough to warrant performing a sentinel node biopsy? And how much of a wide local excision can be performed before the normal lymphatic pathways are disrupted, thereby eliminating any useful information from the mapping procedure?
One cannot assume that a positive sentinel node has the same prognostic value as a random single positive lymph node found on an elective lymph node dissection. A sentinel lymphadenectomy will yield an average of about 1.7 nodes1 that the pathologist can then study with serial sectioning and immunohistochemistry, techniques that are impractical to apply to the multiple nodes removed during an elective lymph node dissection. Therefore, the technique of sentinel node mapping may lead to patients who otherwise would not have been identified as node-positive.
An essential question is whether sentinel lymphadenectomy ultimately improves the outcome for patients with melanoma. In the Multicenter Selective Lymphadenectomy Trial, patients with melanoma more than 1 mm are randomized to wide local excision alone or wide local excision plus preoperative lymphatic mapping and sentinel lymphadenectomy.2 A complete lymph node dissection is done for those patients whose sentinel nodes are positive.
In the Sunbelt Melanoma Trial, patients with melanoma more than 1 mm whose only positive node is a single sentinel node are randomized to observation or one year of standard interferon (all other node-positive patients get one year of interferon).3 Patients whose sentinel node is histologically negative but reveals "sub-microscopic" disease (vide infra) are randomized to either observation (the standard arm), complete lymph node dissection, or a complete lymph node dissection followed by one month of high-dose interferon. "Submicroscopic" involvement with melanoma is identified by the reverse-transcriptase polymerase chain reaction for tyrosinase mRNA. These two studies should help define the role of the sentinel node biopsy in melanoma.
The study by Jansen et al excluded patients whose melanoma was less than 1.0 mm. Lesions between 0.75 mm and 1.0 mm are associated with positive sentinel nodes in 4% of cases.4 Therefore, melanomas that are 0.75 mm or deeper can be considered for a sentinel node biopsy. In terms of timing, a sentinel node biopsy is optimally performed after the local biopsy but before the wide local excision disrupts the normal lymphatic channels. However, a sentinel node biopsy may still be informative if a wide local excision was less than 2.0 cm and not in a region of ambiguous drainage such as the trunk or head and neck.5
Sentinel lymph nodes identified within the parotid gland present a problem unique to melanoma of the head and neck. Fortunately, the majority of intraparotid lymph nodes are in the superficial portion of the gland (2-20 nodes) with only 1-4 nodes lying deep to the facial nerve.6 Therefore, when dissection is necessary, superficial parotidectomy with preservation of the facial nerve is usually recommended.6
References
1. Morton DL, et al. Ann Surg 1999;230:453-463.
2. A Clinical Study of Wide Excision Alone Versus Wide Excision with Intraoperative Lymphatic Mapping and Selective Lymph Node Dissection in the Treatment of Patients with Cutaneous Invasive Melanoma; Morton D, principal investigator. (Ongoing study.)
3. A Multicenter Trial of Adjuvant Inteferon alfa-2B for Melanoma Patients with Early Lymph Node Metastasis Detected by Lymphatic Mapping and Sentinel Lymph Node Biopsy; McMasters K, principal investigator. (Ongoing study.)
4. Rammath E, et al. Cancer Control 1997;4:483-490.
5. Kelemen PR, et al. J Am Coll Surg 1999;189:247-252.
6. O’Brien C, et al. In Balch C, Houghton AN, eds. Cutaneous Melanoma, 3rd ed. New York, N.Y.: Lippincott-Raven; 1998:252-253.
Which one of the following is true?
a. In melanoma, a sentinel lymph node biopsy should be performed in lesions of any depth.
b. Sentinel nodes within the parotid gland are usually negative and therefore need not be removed.
c. Anatomical considerations can complicate the location of
sentinel nodes in the head and neck.
d. Performing sentinel lymph node biopsies has been proven to prolong survival in melanoma.
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