Abstract
Background
Sentinel lymph node biopsy (SLNB) for primary cutaneous head and neck melanoma (CHNM) has been shown to be successful and is the current standard of care for intermediate-thickness melanoma. We evaluated our experience with CHNM associated with SLNB mapping to the region of the parotid gland.
Methods
Retrospective review of a prospectively collected melanoma database identified 1014 CHNMs. Two-hundred twenty-three patients underwent SLNB, and 72 (32%) had mapping in the region of the parotid gland between May 1995 and June 2003.
Results
The mean number of SLNs per patient was 2.5. A sentinel lymph node (SLN) was successfully identified in 94% of patients, and in 12%, the SLN was positive for metastatic disease. Biopsy of intraparotid SLNs was performed in 51.4% and of periparotid SLNs in 26.4%, and a superficial parotidectomy was performed in 22.2%. Ten patients were found to have lymph nodes in the parotid region with metastatic disease (eight identified by SLNB), and two (20%) patients developed intraparotid lymph node recurrence in the setting of a negative SLNB. Same-basin recurrence in SLN-negative patients was 3.3% with a median follow-up of 26 months. Facial nerve dysfunction was identified in seven (10%) patients. Facial nerve function returned to preoperative status in all patients.
Conclusions
SLNB for patients with primary CHNM mapping to the parotid gland can be performed with a high degree of accuracy and a low morbidity consisting of temporary facial nerve paresis.
Keywords: Malignant melanoma, Sentinel node, Parotid gland, Facial nerve
Morton et al.1 described lymphatic mapping and sentinel lymph node biopsy (SLNB) as a low-morbidity procedure with a high degree of accuracy for identifying micrometastatic disease in high-risk patients with clinically negative lymph nodes. These patients are likely to benefit from completion lymphadenectomy. The same group of authors identified sentinel lymph nodes (SLNs) in 90% of the regional nodal basins in patients with stage I head and neck melanoma. Fifteen percent of these nodes were tumor positive, thus indicating the need for completion lymph node dissection. There were no false-negative SLNs, and there was no same-basin recurrence in SLN-negative patients. The authors concluded that SLNB is a minimally invasive and highly accurate screening technique for determining which patients have subclinical node metastases. Thus, they were able to determine which group of patients might benefit from definitive lymph node dissection.2 After these reports, other authors reported their experiences in patients with primary cutaneous head and neck melanomas (CHNM), with low morbidity and an increased SLN identification rate (95%–100%). SLNB has become a viable diagnostic and therapeutic option in the treatment of patients with CHNM melanoma of intermediate thickness.3–8
SLNB of the head and neck presents a number of complex issues. Among these factors are the complex and sometimes unpredictable lymphatic drainage and multiple SLNs per patient,9–11 the proximity of the injection site to the draining basins,3,6 mapping to the parotid gland,3,12 and a slightly greater risk of false-negative results.13 SLNs mapping to the parotid region in patients with CHNM have been reported6–8,13,14 in between 19% and 44% of cases. Ollila et al.3 and Wells et al.12 reported their series with CHNM mapping to the parotid gland and demonstrated that SLNB can be performed accurately and with low morbidity. Morbidity consisting of facial nerve weakness has been reported in the range of 0% to 27% in patients undergoing SLNB in the parotid region.3,5–8,12,13 The objectives of this study were (1) to report our experience with SLNB for CHNM mapping to the parotid gland at a single institution; (2) to examine the accuracy, sensitivity, same-basin recurrence, and morbidity associated with the procedure; and, specifically, (3) to examine the morbidity secondary to facial nerve injury.
PATIENTS AND METHODS
Retrospective review of a prospectively collected melanoma database of our institution identified 1014 CHNMs. Two-hundred twenty-three patients underwent SLNB, and 73 (33%) had preoperative lymphoscintigraphy (PLSG) and intraoperative lymphatic mapping to the region of the parotid gland between May 1995 and June 2003. One patient underwent SLNB at an outside institution, and that patient was excluded from this analysis. We excluded patients with clinically palpable lymph nodes and patients who had already undergone wide local excision associated with a reconstructive procedure, such as a skin graft, rotational skin flap, or other surgical procedure that could interfere with the lymphatic drainage from the primary tumor. Clinical data, surgical details, histopathologic characteristics, and outcome were prospectively entered into a melanoma database, and patients with SLN mapping to the parotid region (n = 72) formed the basis of this analysis.
Preoperative Lymphoscintigraphy
PLSG was used in all 72 patients to identify nodal basins at risk and to identify other sites of nonanatomical uptake. Briefly, .05 mCi (1.9 MBq) of radiation 99mTc sulfur colloid (CIS-US, Inc., Belford, MA) filtered through a .22-μm filter in a volume of .4 mL was injected into four quadrants of the primary lesion or around the previous biopsy site or primary tumor. Injections were performed the morning of the planned surgical procedure, and dynamic scans of all nodal basins at risk were obtained beginning immediately after injection at a rate of one frame per minute for approximately 10 minutes. Anterior and lateral static images were obtained at 5-minute intervals for 20 minutes to 2 hours. A radioactive lead marker was placed in selected patients in the external auditory canal to provide orientation in interpretation of the images. The PLSG was reviewed and discussed with the nuclear medicine physician who performed the study. Basins outside the parotid gland or on the contralateral side were considered separately.
Intraoperative Lymphatic Mapping and SLNB
The SLNB was performed within 4 hours of injection of the radiocolloid, and images were used to guide the procedure in the operating room. Our standardized approach for SLNB includes equipment for injection of 1% isosulfan blue dye (Lymphazurin; Hirsh Industries, Inc., Richmond, VA) and localization of the radioactive colloid. A tuberculin syringe was used to inject the blue dye in an intradermal plane on the side of the lesion nearest to the relevant draining nodes identified by PLSG. Most commonly, a volume of ≤.5 mL was used, because larger volumes tend to dissipate into the subcutaneous tissue and cause artifacts, thus complicating the procedure. A handheld gamma probe (Neoprobe 1000 [Neoprobe Corp, Dublin, OH] or C-Track [Case Wide Medical Products Corp., Morgan Hill, CA]) was used to measure radioactivity counts over the SLNs and to record the background and correlated with the PLSG findings. The gamma probe was used to measure the ex vivo radioactivity of the SLN. Reduction of the background activity of the basin to < 10% of the hottest SLN was considered as indicative of excision of all SLNs. While the SLN was undergoing frozen-section analysis, the primary melanoma or surgical scar was excised by using margins according to the depth of invasion and the site of the lesion. If histopathologic examination revealed metastatic disease, parotidectomy with preservation of the facial nerve and ipsilateral modified radical neck dissection was performed as an immediate completion lymph node dissection.
Histopathologic Examination of SLNs
Frozen-section analysis was performed in all patients. Each SLN sent to pathology was bisected from the hilum to its periphery. Half of the node was immediately processed for frozen-section analysis by using routine hematoxylin and eosin staining, and the other half was processed for immunohistochemical staining by using antibodies to S-100 protein and HMB-45. All lymphatic and parotid tissues were embedded in paraffin and sectioned according to routine departmental protocol.
Statistical Methods
Data were analyzed with a statistical package (SPSS 12; SPSS Inc., Chicago, IL). Follow-up was calculated in months from the date of SLNB to the date of last follow-up or death, and the disease-free interval was calculated from the date of SLNB to the date of first recurrence.
RESULTS
Patient demographic data and primary tumor characteristics are listed in Table 1. The median age was 62 years, and most patients (76%) were male. Sixty-three percent of primary melanomas were located on the face. The most common sites on the face were the forehead (15%), cheek (15%), and temple (15%). Nonfacial sites occurred in 37%, and of those, the most common site was the ear (22%). The median Breslow thickness was 2.0 mm (range, 1–10 mm), and most (64%) were Clark level IV. Five (7%) patients had T1 tumors (≤1 mm thick), and of those five patients, three were Clark level IV and the other two were Clark levels II and III. The last two patients did not meet the 2005 National Comprehensive Cancer Network Clinical Practice Guidelines for SLNB.
TABLE 1.
Patient and primary tumor characteristics (n = 72)
| Variable | Data |
|---|---|
| Age (y) | |
| Median | 62 |
| Range | 14–96 |
| Sex | |
| Female | 17 (24) |
| Male | 55 (76) |
| Localization | |
| Facial, n = 45 (63%) | |
| Forehead | 11 (15) |
| Cheek | 11 (15) |
| Temple | 11 (15) |
| Preauricular | 6 (8) |
| Nasolabial crease | 2 (3) |
| Mandibular border | 2 (3) |
| Lateral canthus | 1 (2) |
| Eyebrow | 1 (2) |
| Nonfacial, n = 27 (37%) | |
| Ear | 16 (22) |
| Scalp, coronal | 4 (5) |
| Neck, anterior-superior | 2 (3) |
| Scalp, anterior | 2 (3) |
| Scalp, posterior | 2 (3) |
| Retroauricular | 1 (1) |
| Stage (AJCC 2002) | |
| IA | 4 (6) |
| IB | 27 (38) |
| IIA | 13 (18) |
| IIB | 14 (19) |
| IIC | 5 (7) |
| IIIA | 4 (6) |
| IIIB | 4 (5) |
| IIIC | 1 (1) |
| Histology | |
| Malignant melanoma, NOS | 49 (68) |
| Nodular | 8 (11) |
| Superficial spreading | 4 (6) |
| Desmoplastic | 4 (6) |
| Lentigo maligna | 2 (3) |
| Superficial spreading + nodular | 2 (3) |
| Lentigo maligna + desmoplastic | 2 (2) |
| Spitz nevus | 1 (1) |
| Ulceration | 20 (28) |
| Breslow thickness (mm) | |
| <.75 | 4 (6) |
| .75–1.5 | 19 (26) |
| 1.5–4 | 30 (42) |
| >4 | 19 (26) |
| Clark level | |
| II | 1 (1) |
| III | 8 (11) |
| IV | 46 (64) |
| V | 11 (15) |
| Unknown | 6 (8) |
| Lymphovascular invasion | 4 (6) |
| Perineural invasion | 5 (7) |
| Tumor-infiltrating lymphocytes | 39 (54) |
| Regression | 11 (15) |
| Associated nevus | 5 (7) |
| Type of first biopsy | |
| Excisional | 32 (45) |
| Shave | 25 (35) |
| Punch | 8 (11) |
| Incisional | 1 (1) |
| Unknown | 6 (8) |
| Presence of residual melanoma in second resection specimen | 35 (49) |
Data are n (%) unless otherwise noted.
AJCC, American Joint Committee on Cancer; NOS, not otherwise specified.
PLSG was performed in all patients (Table 2). In five (7%) patients, PLSG failed to identify an area of uptake. Ninety-two different areas of uptake were identified in 67 patients, with a mean of 1.4 areas of uptake per patient. The most common site of uptake was the parotid gland, with 82% of cases mapping to the parotid region. Contralateral uptake occurred in three (4%) patients, two of whom had primary tumors in the midline of the forehead and one in the midline apex of the scalp. All three contralateral SLNs were negative for metastatic disease. In four of five patients in whom the PLSG failed to identify areas of uptake, the SLN was identified by using isosulfan blue dye. In the other patient, the primary tumor was located in the preauricular region, and because of the proximity to the parotid gland, a superficial parotidectomy was performed. With both PLSG and intraoperative lymphatic mapping, SLNs were identified in the parotid basin in 94.5%, and the procedure was unsuccessful in 5.5% of patients (Table 2). Of the four patients with a positive PLSG to the parotid gland and unsuccessful intraoperative mapping, three underwent superficial parotidectomy, and in one of these patients, the parotidectomy specimen revealed metastatic disease. One hundred sixty-eight SLNs were identified, with a mean of 2.5 nodes per patient (range, 1–6). Twenty-one percent of patients had one SLN, 41% had two, and 38% had three or more SLNs identified. Four patients had metastatic disease on frozen section, and all of them underwent superficial parotidectomy and ipsilateral modified radical neck dissection (MRND; Table 3).
TABLE 2.
Details of PLSG and SLN biopsy (n = 72)
| Variable | n (%) |
|---|---|
| Lymphoscintigraphy localization: 92 areas of uptake identified in 67 patients (1.4 areas per patient) | |
| Parotid | 55 (60) |
| Level I | 12 (13) |
| Level II | 17 (19) |
| Level III | 1 (1) |
| Level IV | 1 (1) |
| Level V | 1 (1) |
| Supraclavicular | 3 (3) |
| Retroauricular | 1 (1) |
| Suboccipital | 1 (1) |
| Not identified | 5 (7) |
| Technique | |
| Blue dye alone | 0 (0) |
| Technetium alone | 12 (17) |
| Both | 60 (83) |
| Identification | |
| Success | 68 (94) |
| Failure | 4 (6) |
| Contralateral side | 3 (4) |
| No. of SLNs identified (mean, 2.5) | |
| 1 | 14 (21) |
| 2 | 28 (41) |
| 3 | 12 (17) |
| 4 | 9 (13) |
| 5 | 4 (6) |
| 6 | 1 (2) |
| Positive SLN, frozen section | 4 (6) |
| Negative SLN, frozen section | 64 (94) |
| Positive SLN, permanent section | 8 (12) |
| Negative SLN, permanent section | 60 (88) |
| Sensitivity (%) | 50 |
| Specificity (%) | 100 |
| Positive predictive value (%) | 100 |
| Negative predictive value (%) | 94 |
PLSG, preoperative lymphoscintigraphy; SLN, sentinel lymph node.
TABLE 3.
Treatment of patients with parotid lymph nodes positive for metastatic disease
| Patient no. | SLN frozen | SLN permanent | Treatment | Pathology | Site of recurrence | Surgical treatment of recurrent disease |
|---|---|---|---|---|---|---|
| 1 | Pos | Pos | Parotidectomy and MRND (levels I–V) | 2 Pos LNs, supraclavicular | Liver | – |
| 2 | Pos | Pos | Parotidectomy and MRND (levels I–V) | 2 Pos LNs, level I | Liver, distant soft tissue | – |
| 3 | Pos | Pos | Parotidectomy and MRND (levels I–V) | Neg | – | – |
| 4 | Pos | Pos | Parotidectomy and MRND (levels II–III) | Neg | – | – |
| 5 | Neg | Pos | Parotidectomy and MRND (levels I–V) | Neg | – | – |
| 6 | Neg | Pos | No further treatment | – | – | – |
| 7 | Neg | Pos | No further treatment | – | – | – |
| 8 | Neg | Pos | No further treatment | – | – | – |
| 9 | Neg | Neg | – | – | Intraparotid LN | Parotidectomy and MRND (levels I–V) |
| 10 | Neg | Neg | – | – | Intraparotid LN | Parotidectomy and MRND (levels I–V) |
SLN, sentinel lymph node; Pos, positive for metastases; MRND, modified radical neck dissection; Neg, negative for metastases; LN, lymph node.
There was no residual metastatic melanoma in the parotid specimens, but in two of these four patients, the final histopathologic analysis revealed metastatic melanoma in the MRND specimens. Four (6%) patients had a negative frozen-section SLN biopsy for metastatic disease, but on permanent section, including immunohistochemistry analysis, they had micrometastatic disease. One of these patients subsequently underwent superficial parotidectomy and MRND (levels I through V), and all nodes were negative for metastatic disease. The other three patients did not undergo additional node dissection. On the basis of our retrospective review of medical records, it was difficult to infer whether the decision for observation was the surgeon’s or the patient’s decision. None of these four patients developed recurrent disease (Table 3). Sixteen (22%) patients underwent subtotal parotidectomy for different reasons as part of the SLNB. In three patients, the SLN was not identified; four patients had positive frozen-section results for metastatic disease; four patients had positive frozen-section results for residual bed counts; four had positive frozen-section results for multiple intraparotid SLNs; and in one patient, the primary tumor was located in the preauricular region, and there was no uptake on PLSG.
The seventy-two patients had a median follow-up of 26 months (range, 3–87 months), and six (8%) developed locoregional recurrences. One (1.4%) developed an isolated local recurrence on the cheek, and three (4%) patients developed lateral neck recurrences (Table 4). Two (3.3%) of 60 SLN-negative patients developed same-basin recurrence in the parotid gland 5 and 11 months after the SLNB. Both patients subsequently underwent superficial parotidectomy and MRND, and pathologic analysis revealed only one intraparotid lymph node positive for metastatic disease in both patients. Both patients with same-basin recurrence at the time of the SLNB had both frozen- and permanent-section analysis negative for metastatic disease. Ten patients had parotid basin lymph nodes with metastatic disease, eight as a consequence of SLNB, and two (20%) patients developed intraparotid lymph node recurrence. The last two patients represent a more accurate false-negative rate for parotid SLNB. Five (7%) patients developed systemic recurrence. The median time to first recurrence for both locoregional and systemic recurrent disease was 15 months (Table 4). There were no major complications or deaths related to the procedures (SLNB, parotidectomy, and MRND). The most significant morbidity was related to facial nerve dysfunction (Table 5). Seven (10%) patients with facial nerve weakness were identified, and all recovered normal facial nerve function during the first year after surgery. Only 2 (5%) of 37 patients undergoing intraparotid SLNB developed paresis of the marginal branch of the facial nerve, and all recovered to normal function. All branches of the facial nerve were paretic in 4 (25%) of 16 patients who underwent superficial parotidectomy, and 1 (6%) patient had complete paralysis of the facial nerve that recovered to preoperative status by the third postoperative visit at 6 months. Nineteen patients underwent SLNB of periparotid lymph nodes, and none of them developed nerve weakness. There were no cases of permanent facial nerve paralysis, Frey’s syndrome, or injury to Stensen’s duct.
TABLE 4.
Patterns of recurrence
| Site of first recurrence | SLN | n | % | Time to recurrence (mo) |
|---|---|---|---|---|
| Locoregional | 6 | 8 | ||
| Cheek (local) | Neg | 1 | 1.4 | 17 |
| Parotid basin | Neg | 2 | 2.8 | 5 and 11 |
| Level II | Neg | 1 | 1.4 | 12 |
| Level II–V | Pos | 1 | 1.4 | 19 |
| Level III | Neg | 1 | 1.4 | 57 |
| Systemic | 5 | 7 | ||
| Brain | Neg | 2 | 2.8 | 7 and 29 |
| Liver | Pos | 1 | 1.4 | 6 |
| Lung | Neg | 1 | 1.4 | 15 |
| Liver + distant soft tissue | Pos | 1 | 1.4 | 40 |
| Total | 11 | 15 | Median: 15 mo |
SLN, sentinel lymph node; Neg, negative for metastases; Pos, positive for metastases.
TABLE 5.
Facial nerve injury
| Procedure (n = 72) | Facial nerve affected | Facial nerve function | Postoperative visit (%)a | ||
|---|---|---|---|---|---|
|
| |||||
| 1 | 2 | 3 | |||
| Intraparotid LN biopsy (n = 37) | Mandibular branch (n = 2) | Normal | 94 | 97 | 100 |
| Paresis | 6 | 3 | 0 | ||
| Paralysis | 0 | 0 | 0 | ||
| Parotidectomy (n = 16) | All branches affected (n = 5) | Normal | 70 | 94 | 100 |
| Paresis | 24 | 6 | 0 | ||
| Paralysis | 6 | 0 | 0 | ||
| Periparotid LN biopsy (n = 19) | None | Normal | 100 | 100 | 100 |
| Total | Injury: 7 (10%) | Normal | 90 | 97 | 100 |
LN, lymph node.
Postoperative visits: 1, first 2 weeks; 2, 3 months; 3, 6 months.
DISCUSSION
Preceding the SLNB era, patients with CHNM with clinically negative nodes and patients with palpable lymph nodes in the region of the parotid gland underwent elective or therapeutic parotidectomy and ipsilateral MRND, respectively.9,15,16 Caldwell and Spiro15 reported 65 patients who underwent parotidectomy as part of the treatment for CHNM. Forty-three patients (66%) underwent elective lymph node dissection (ELND), and 31 (72%) had parotid nodes positive for metastatic disease. Only one patient with locoregional failure experienced recurrence within the parotid bed. Permanent partial or total facial nerve damage was observed in 27 (42%) patients. Vaglini et al.17 reported similar findings in 46 patients with CHNM. Thirty-five percent underwent elective parotidectomy and lymphadenectomy. Thirty-one percent of ELND specimens had lymph nodes positive for metastatic melanoma. Temporary facial nerve injury occurred in 12 (26%) patients, and 1 (2%) patient had a permanent deficit. In 1994, O’Brien et al.16 reported 107 therapeutic and elective parotidectomies for CHNM. Six percent of the elective dissections were found to have lymph nodes positive for meta-static melanoma. Sixty-seven (69%) and 10 (9%) patients with temporary and permanent facial nerve damage, respectively, were reported. These reports demonstrate a high incidence of pathologically positive lymph nodes in ELND specimens that may not be clinically relevant in terms of survival, because it has been shown in randomized and retrospective studies that ELND for intermediate-thickness melanoma may not improve survival.18–22 This radical surgery carries the risk of morbidity associated with facial nerve and other cranial nerve dysfunction.
SLNB in the management of intermediate-thickness CHNM with clinically negative nodes minimizes the morbidity of ELND in patients without metastatic disease. Gershenwald et al.,23 in a multi-institutional SLNB experience for stage I and II in patients with cutaneous melanoma, showed that the SLN pathologic status was the most significant prognostic factor with respect to disease-free and disease-specific survival by univariate and multivariate analysis. They concluded that SLNB is highly accurate in staging nodal basins at risk for regional metastases in primary melanoma patients and that it identifies those who may benefit from earlier lymphadenectomy. The reliability and safety of the procedure have been analyzed in many prospective and retrospective studies. Eicher et al.,14 in a prospective study, reported an SLN identification rate of 98% of 43 patients, with a mean of 3.6 SLNs per patient. Twenty-one percent had metastatic disease in the SLN, and no patient with a negative SLN had a positive non-SLN. The authors did not report same-basin recurrence in SLN-negative patients. Schmalbach et al.24 reported a cohort of 80 patients with CHNM, with a 96.3% SLN identification rate and no facial nerve complications. The regional failure rate in SLN-negative patients was 4.5%. A review of other institutional experiences and the results of our current analysis in the use of SLNB for CHNM are presented in Table 6. These reports demonstrate that SLNB in patients with primary CHNM is reliable and can accurately predict the status of the nodal basin with minimal procedure-associated morbidity.
TABLE 6.
Published results of SLNB in CHNM
| Variable | Bostick et al.26 (1997) | Ollila et al.3 (1999) | Wells et al.12 (1999) | Wagner et al.5 (2000) | Carlson et al.6 (2000) | Patel et al.8 (2002) | Chao et al.13 (2003) | Fincher et al.7 (2004) | Present series |
|---|---|---|---|---|---|---|---|---|---|
| No. of CHNMs | 117 | 39 | 28 | 70 | 58 | 56 | 321 | 51 | 72 |
| SLNs mapping to the parotid (%) | NA | 100 | 100 | NA | 24 | 27 | 26 | 35 | 100 |
| Overall results, SLNB (%) | |||||||||
| Failure | 7 | 5 | 14 | 1 | 4 | 7 | 3 | 0 | 6 |
| Success | 93 | 95 | 86 | 99 | 96 | 93 | 97 | 100 | 94 |
| SLNs per patient, range (mean) | 1 | 1–4 (2.3) | NA | 1–8 | −2.7 | 1–11 (2.6) | −2.8 | −2.75 | 1–6 (2.5) |
| Positive SLN, n (%) | 11 (12) | 4 (11) | 4 (17) | 12 (17) | 10 (18) | 4 (8) | 43 (15) | 8 (16) | 8 (12) |
| Same-basin recurrence in SLN-negative patients, n (%) | All NED | 1/33 (3) | 2/20 (10) | 1/58 (2) | 1/47 (2) | 1/48 (2) | 6/321 (2) | 0 | 2/60 (3) |
| False negatives, n (%)a | 0 | 1/5 (20) | 2/6 (33) | 1/13 (8) | 1/11 (9) | 1/5 (20) | 6/49 (12) | 0 | 2/10 (20) |
| Facial nerve dysfunction, n (%) | |||||||||
| Temporary | 1 (2.6) | 0 | 2 | 0 | 4 (27%) | 1 | 0 | 7 (10) | |
| Permanent | NA | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 |
SLNB, sentinel lymph node biopsy; CHNM, cutaneous head and neck melanoma; SLN, sentinel lymph node; NA, not available; NED, no evidence of disease.
False negative: parotid basin lymph node metastasis missed by SLNB.
One of the most common means of reporting false-negative rates for SLNB is to determine the same-basin recurrence rate for SLN-negative patients. Same-basin recurrence rates vary according to the primary tumor site. Chao et al.,13 from the Sunbelt Melanoma Trial, reported a total of 2610 patients with a median follow-up of 18 months and a false-negative rate of 1.9% for head and neck and .5% for trunk and extremity melanomas (P < .05). Different studies with variable median follow-up (range, 11–21 months) have reported same-basin recurrence in the range of 0% to 10.5%.3,12,25 The differences in results can be attributed to differences in technique and follow-up periods. Differences according to the site of the primary tumor can be explained by more predictable lymphatic drainage in patients with extremity and trunk melanoma. Patients with SLN mapping to the parotid region have a higher same-basin recurrence rate (3.1%–7%)3,12 compared with other sites, including other CHNMs not mapping to the parotid region.4,7,8,26 Our analysis demonstrates a same-basin recurrence rate in SLN-negative patients of 3.3% and is consistent with other reports. We believe that the most accurate method of reporting false-negative results is to report the number of parotid basin lymph node metastases missed by the SLNB. In this study, we identified two (20%) patients who developed intraparotid recurrence out of 10 patients with lymph nodes positive for metastatic disease in the parotid basin. This implies that 20% of this subset of patients will require superficial parotidectomy and MRND as a secondary procedure.
It is interesting to note that patients with head and neck melanomas had a 15% rate for positive SLNs for metastatic disease, whereas trunk and extremity melanoma had 23.4% and 19.5% rates, respectively.13 Our own institutional SLNB experience for all sites was reported with a 17% rate for positive SLNs.27 The incidence of SLNs positive for metastatic disease in CHNM has been reported between 8% and 18%.3,6,8,12,27 This lower incidence in the number of positive SLNs can be attributed, among other above-mentioned factors, to the increased number of desmoplastic melanomas (DM) in the head and neck area. Series from our institution have reported that DM occurs in < 2% of all melanomas seen at Memorial Sloan-Kettering Cancer Center28 and with a very low incidence of lymph node metastases.29 In this series, we report 8% DM, which could be responsible for the lower incidence (12%) of SLNs positive for metastatic disease. Another factor that may have altered the low incidence of lymph node metastasis in our series was the inclusion of two (3%) patients with Clark level II and III without ulceration. These two patients did not meet the 2005 National Comprehensive Cancer Network guidelines for SLNB currently followed at our institution. This was a retrospective analysis, and it is difficult to determine why these two patients were mapped.
CHNM mapping to the parotid gland represents a distinct group of patients with more complex lymphatic drainage. A positive SLN implies the need for completion parotidectomy and ipsilateral MRND, with the risk of facial nerve injury. Ollila et al.3 reported the experience in 39 patients with CHNM and SLNB mapping to the parotid gland. They were able to identify an SLN in 95% and failed to identify it in 5%. The latter patients underwent superficial parotidectomy with no evidence of metastatic melanoma. The mean number of SLNs was 2.3 per patient (range, 1–4). A positive SLN for metastatic disease was identified in 4 (11%) of 37 patients in whom the SLN was identified. Completion parotidectomy and MRND revealed no residual metastatic disease of the parotid gland and in two of four of the MRND specimens exhibited metastatic disease. With a median follow-up of 33 months, only 1 (3.1%) of 33 SLN-negative patients developed a same-basin recurrence. The authors concluded that sentinel lymphadenectomy in the parotid region is an accurate staging method and offers a low-morbidity alternative to elective superficial parotidectomy and cervical lymphadenectomy. Wells et al.12 reported 28 patients with primary CHNM that on PLSG demonstrated lymphatic drainage to the parotid gland. The SLN identification rate was 86%, with 4 (17%) of 24 patients with SLNs positive for metastatic disease. After therapeutic parotidectomy, one of four patients was found to have a non-SLN with metastatic melanoma. With a median follow-up of 12 months, 2 (10%) of 20 patients with negative SLNs developed same-basin recurrence. The authors concluded that SLNB is a reliable alternative to superficial parotidectomy for staging CHNM mapping to the parotid region.
The intraoperative frozen-section analysis of the SLN can underestimate the true incidence of metastasis, and false-negative SLNs may contain microscopic metastatic disease that may not be identified in the examined histological slides.30 In the series reported by Ollila et al.3 in which SLN frozen-section analysis was used, two of four patients had positive frozen-section results for metastatic disease, and in two SLNs, metastatic disease was confirmed by immunohistochemistry staining. Wells et al.12 did not use frozen-section analysis, and four patients had positive SLNs with micrometastases by immunohistochemistry. All four patients subsequently underwent parotidectomy and MRND. In this series, we routinely used frozen-section analysis with a sensitivity of 50% and a specificity of 100%. Those with positive SLNs on frozen section underwent immediate parotidectomy and MRND. This is extremely important in our patient population because it obviates the need for secondary operation in half of the patients: performing parotidectomy and MRND in patients who have had a previous modified Blair incision is extremely difficult. We believe that a secondary procedure puts these patients at additional risk for facial nerve injury.
Facial nerve function after SLNB in patients with CHNM has not been consistently reported. Many series have not reported the status of the facial nerve,4,14,25,26 and in others the facial nerve injury rate varies considerably (0%–27%). This variability leads us to surmise that in many series, facial nerve function has not been part of the analysis and has been underreported. Patel et al.8 reported 15 patients who had SLNs that mapped to the parotid region. These patients were included in the current series. Six (40%) patients underwent subtotal parotidectomy, and in nine (60%) patients, only the SLN was sampled. Temporary facial nerve weakness was identified in 4 (27%) of the 15 patients, and all 4 regained complete function. Three of these four underwent parotidectomy with identification of all branches of the facial nerve, and in one patient with an intraparotid biopsy of the SLN, transient facial nerve paresis was noted. Ollila et al.3 reported one (3%) patient with temporary facial nerve paresis that completely resolved and no cases of permanent nerve paralysis. Wells et al.12 reported one patient in whom the buccal branch of the facial nerve was partially transected and repaired with no long-term sequelae. In this study, we specifically analyzed facial nerve function. Two (5%) of 37 patients who underwent intraparotid SLNB developed paresis of the marginal branch, 4 (25%) of 16 patients undergoing superficial parotidectomy developed paresis of all branches of the facial nerve, and 1 (6%) had paralysis after parotidectomy. All patients recovered complete facial nerve function by the third postoperative visit. None of 39 patients undergoing periparotid SLNB developed any facial nerve dysfunction. This confirms the results of other series that facial nerve damage can occur, that temporary paralysis of the facial nerve is usually associated with superficial parotidectomy, and that intraparotid or periparotid SLNB is associated with a low incidence of facial nerve damage.
Reported patterns of recurrence and rates of recurrence in SLN-negative patients are variable, ranging from 0% to 25%,4,8,10,12 and the most important reason for the variability is attributed to the follow-up period. Fincher et al.,7 in a series of 51 patients with clinically negative CHNM and a mean follow-up of 35 months, found a recurrence rate of 7%. There were no same-basin recurrences in SLN-negative patients, and the 36-month disease-specific survival was 89% in SLN-negative patients and 73% for patients with positive SLNs (P = .17). In the same study, patients with recurrent disease had a greater mean melanoma thickness and a higher percentage of positive SLNs. However, on multivariate analysis, none of the covariates was statistically significant. Patel et al.8 reported a 7% recurrence rate, and the presence of metastatic disease in the SLNs was not a statistically significant predictor of 2-year disease-specific survival (93.2% in SLN-negative patients vs. 50% in SLN-positive patients; P = .20). In our group of patients, with a median follow-up of 26 months and a median time to recurrence of 15 months, 11 (15%) developed recurrence. Three (4%) patients developed recurrent nodal disease in the neck (12–57 months), and five (7%) patients developed systemic recurrence (6–40 months). Long-term follow-up is warranted to detect recurrent disease years after resection of the primary tumor, independently of the status of the SLNB at the time of the first resection.
In summary, patients with primary CHNMs mapping to the parotid region are a unique group because of the anatomical location of the SLNs, unpredictable pattern of lymphatic drainage, and proximity to the primary site. Despite the fact that SLNs in this region have a slightly higher same-basin recurrence rate compared with CHNM not mapping to the parotid region or truncal melanoma, SLNB continues to be a reliable staging procedure for intermediate-thickness melanoma. The major issue in performing SLNB in the parotid gland and the periparotid lymph nodes is the facial nerve. This experience documents that in the hands of experienced head and neck surgeons, acceptable oncological outcomes and long-term facial nerve function can be obtained with an acceptable incidence of temporary facial nerve dysfunction.
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