LYMPHATIC DRAINAGE PATTERNS OF HEAD AND NECK CUTANEOUS MELANOMA OBSERVED ON LYMPHOSCINTIGRAPHY AND SENTINEL LYMPH NODE BIOPSY

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1 LYMPHATIC DRAINAGE PATTERNS OF HEAD AND NECK CUTANEOUS MELANOMA OBSERVED ON LYMPHOSCINTIGRAPHY AND SENTINEL LYMPH NODE BIOPSY Doris Lin, MD, 1 Benjamin L. Franc, MD, 2 Mohammed Kashani-Sabet, MD, 3 Mark I. Singer, MD 1 1 Department of Otolaryngology Head and Neck Surgery, University of California, San Francisco, 2380 Sutter Street, Box 1703, San Francisco, CA msinger@ohns.ucsf.edu 2 Department of Radiology, University of California, San Francisco, San Francisco, California 3 Melanoma Center, Department of Dermatology, University of California, San Francisco, San Francisco, California Accepted 21 July 2005 Published online 24 January 2006 in Wiley InterScience ( DOI: /hed Abstract: Background. The purpose of this study was to evaluate lymphatic drainage patterns of head and neck cutaneous melanoma observed on preoperative lymphoscintigraphy and sentinel lymph node biopsy (SLNB) and determine discordancy from clinically predicted lymphatic drainage patterns. Methods. We conducted a retrospective chart review of 114 patients with head and neck cutaneous melanomas evaluated with preoperative lymphoscintigraphy and SLNB from January 2001 through July Results. At least one sentinel lymph node (SLN) was identified in 97% of cases. On preoperative lymphoscintigraphy, an SLN was identified in an area not clinically predicted in 49 cases (43%). The most common sites of discordancy were in areas not typically dissected in standard neck dissections, such as the postauricular region, or in areas of more distant drainage than described previously, such as the inferior or posterior neck. Their percentages of discordant cases were 51%, 27%, and 22%, respectively. The sites of regional recurrence occurred in two cases not predicted on preoperative lymphoscintigraphy and in two cases of failed SLNB. Correspondence to: M. I. Singer Presented at Fourth International Sentinel Node Congress, Los Angeles, California, December 3 5, B 2006 Wiley Periodicals, Inc. Conclusions. On the basis of preoperative lymphoscintigraphy and the results of SLNB, head and neck cutaneous melanomas do have expected lymphatic drainage patterns despite perceived discordancy with previously clinically predicted drainage patterns that are based on standard neck dissection specimens. These discordant sites can still harbor melanoma, and all sites predicted on preoperative lymphoscintigraphy still need to be explored. The four cases of recurrences underscore the importance of close follow-up for all patients regardless of the SLNB result. A 2006 Wiley Periodicals, Inc. Head Neck 28: , 2006 Keywords: sentinel lymph node; dissection; head and neck; lymphoscintigraphy; cutaneous malignancy; melanoma; lymph node; biopsy; lymphatic drainage Nodal status has been recognized as the most significant prognostic factor for patients diagnosed with cutaneous melanoma, the most deadly form of skin cancer. 1 3 However, elective regional node dissection has not been shown to definitely improve survival among patients with cutaneous melanoma from any site. 4 6 Most patients with cutaneous melanoma do not harbor nodal metastasis, potentially placing these patients at increased, but unnecessary, morbidity with an Lymphatic Drainage Patterns in SLNB HEAD & NECK March

2 elective regional node dissection. Although lesions less than 1 mm thick are associated with a less than 5% rate of regional metastasis, lesions thicker than 4 mm are associated with a 30% to 50% rate of nodal involvement. For lesions in the intermediate range, the likelihood of lymph node metastasis is approximately 20%. 2 To address the need for prognostic information from lymph node status in this intermediate group but with a minimally invasive procedure, Morton et al 7 introduced sentinel lymph node biopsy (SLNB) to identify patients with trunk and extremity cutaneous melanoma harboring occult nodal disease but using a minimally invasive procedure. The technique of lymphoscintigraphy has enhanced and improved the safety and reliability of the SLNB procedure. 7 9 However, lymphoscintigraphy has often predicted drainage outside of the usual drainage patterns, which may or may not be clinically significant, particularly in the head and neck region In this study, we describe the lymphatic drainage patterns of head and neck cutaneous melanoma predicted by lymphoscintigraphy, identify areas of discordancy from patterns previously predicted clinically, and correlate these findings with the clinical outcome of our patients. MATERIALS AND METHODS The University of California, San Francisco (UCSF) Committee on Human Research granted approval for this study. A retrospective chart review of 114 patients treated for head and neck cutaneous melanoma with staging by SLNB at UCSF was performed. Patients were identified by searching the UCSF Department of Otolaryngology, Head and Neck Surgery computer database from January 2001 through July All patients with histologically proven melanoma with a minimum Breslow thickness of 1.00 mm (or <1.00 mm if other adverse prognostic variables such as tumor ulceration, extension to deep margin, or Clark level IV) with clinically absent regional or distant metastases were evaluated and counseled for SLNB by the UCSF Multidisciplinary Melanoma Tumor Board. All patients underwent preoperative lymphoscintigraphy, intraoperative lymphatic mapping using 1% Lymphazurin blue dye, and SLNB described previously. 9 Lymphoscintigraphy was performed 2 to 15 hours before surgery by injecting 400 to 1000 ACi of technetium sulfur colloid (in ml) intradermally in four quadrants around the excision site of the primary lesion. Preoperative images of the head and upper thorax were obtained from the anterior, posterior, lateral, and oblique projections using a gamma scintillation camera in the nuclear medicine department. A handheld gamma probe (Neoprobe 2000; Batelle, Columbus, OH) was used intraoperatively to confirm the location of the nodal basins identified by lymphoscintigraphy and to confirm excision of candidate nodes. Intraoperative lymphatic mapping using 1% Lymphazurin blue dye was performed by injecting a total of 1 ml of dye intradermally into the four quadrants surrounding the primary melanoma lesion once general anesthesia was obtained and 15 minutes later. A combination of radioactivity (hot) and/or color (blue) was used to identify the SLN. Completion of dissection was confirmed when all nodal basins had minimal background radioactivity relative to the primary lesion and SLN. After identification of the SLN (defined as a lymph node with direct and independent drainage from the primary site), the primary lesion was excised with 0.5- to 3-cm margins, depending on the location in the head and neck, except for two lesions that had been resected with Mohs technique with at least 1-mm margins before SLNB. All SLNs were sent for histologic evaluation with permanent sections, level sectioned at 5 Am, and stained with hematoxylin eosin (H & E), S-100, and HMB-45. Patients with an SLN positive for metastatic melanoma underwent therapeutic lymphadenectomy or parotidectomy within 2 months after SLNB. Adjuvant therapy, including vaccine, interferon, and/or radiation therapy, was recommended when indicated by the UCSF Multidisciplinary Melanoma Tumor Board. Preoperative lymphoscintigraphy images were reviewed for notable drainage patterns and candidate SLNs. Discordancy was determined by comparing noted drainage with previously described drainage patterns based on neck dissection specimens described by O Brien et al. 10 Any noted drainage outside of predicted areas was considered discordant. Bilateral drainage for midline lesions was not considered discordant. RESULTS One hundred fourteen patients treated for head and neck cutaneous melanoma from January 2001 through July 2004 were included in this study. Ninety-nine patients were men (86%), and 250 Lymphatic Drainage Patterns in SLNB HEAD & NECK March 2006

3 Table 1. Site distribution of primary melanoma lesions in the head and neck. Location of primary No. of cases (%) 1. Anterior scalp 16 (14) 2. Coronal scalp 2 (2) 3. Posterior scalp 20 (18) 4. Preauricular 2 (2) 5. Ear 13 (11) 6. Upper face 29 (25) 6N. Nose 12 (11) 7. Lower face 2 (2) 8. Anterior upper neck 0 (0) 9. Anterior lower neck 2 (2) 10. Coronal upper neck 8 (7) 11. Coronal lower neck 1 (1) 12. Posterior upper neck 6 (5) 13. Posterior lower neck 1 (1) 15 patients were women (13%). The average age was 61 years (range, years). The average Breslow thickness was 2.5 mm (range, mm). The site distribution of primary melanoma lesions is listed in Table 1. Follow-up average was 7 months (range, 0 36 months). Twentyeight patients had less than 1 month of followup (lymphoscintigraphy, SLNB, and pathology results still included in this study). By use of the combination of lymphoscintigraphy, intraoperative gamma probe, and Lymphazurin blue dye, at least one SLN was identified in 111 of 114 cases (97%). The average number of SLNs found was four (range, 1 13). The one patient with 13 SLNs identified, none of which contained melanoma, had a midline forehead lesion with bilateral drainage patterns noted on lymphoscintigraphy all of which were explored and were found to be positive with the gamma probe but were not blue. On preoperative lymphoscintigraphy, at least one SLN was identified in an area not clinically predicted in 49 cases (43%). The sites and areas of drainage are listed in Table 2. These sites were compared with drainage patterns predicted by O Brien et al 10 on the basis of therapeutic and elective neck dissections for cutaneous head and neck melanoma. Areas of discordancy are highlighted in Table 3. The most common sites of discordancy were in areas not typically dissected in standard neck dissections, such as the postauricular (51%), preauricular (6%), occipital (4%), level VI (4%), and axillary (4%) regions. The other areas of discordancy were in sites of more distant drainage than described previously, such as the inferior/level IV (27%) or posterior/level V (22%) neck. There were no cases of contralateral drainage. Fourteen cases (12%) had positive SLNs containing metastatic melanoma (summarized in Table 4). Eleven of these cases have been described previously. 9 In two cases, preoperative lymphoscintigraphy predicted a positive SLN in an area outside of clinically predicted areas (cases 6 and 12). The first case involved a primary melanoma of the upper face metastasizing to the postauricular region (this patient died of unknown causes 4 months later) (Figure 1). The second case Table 2. Nodal drainage distribution on lymphoscintigraphy. Level of Neck Location of primary Predicted (O Brien) 10 I II III IV V VI Parotid/preauricular Postauricular Occipital Axilla 1. Anterior scalp I III, parotid Coronal scalp I V, parotid Posterior scalp II V, occipital Preauricular I III, parotid Ear I V, parotid Upper face I III, parotid N. Nose I III, parotid Lower face I III, parotid Anterior upper neck I IV, parotid Anterior lower neck III V Coronal upper neck I V, parotid Coronal lower neck III V Posterior upper neck II V, occipital Posterior lower neck III V Total Note. Data represent number of cases predicting drainage to that location. Lymphatic Drainage Patterns in SLNB HEAD & NECK March

4 Table 3. Areas of discordancy from predicted drainage patterns. Location of primary Discordancy Postauricular Preauricular Inferior neck (IV) Posterior triangle (V) Occipital Midline (VI) Axilla 1. Anterior scalp 9 (56) 4 (25) 0 4 (25) 4 (25) 2 (13) Coronal scalp 1 (50) 1 (50) Posterior scalp 12 (60) 10 (50) 3 (15) Preauricular 1 (50) (50) Ear 4 (31) 4 (31) Upper face 11 (38) 5 (17) 0 3 (10) 4 (14) N. Nose 6 (50) 1 (8) 0 4 (33) 2 (17) 0 1 (8) 0 7. Lower face 2 (100) (100) Anterior upper neck 0 (0) Anterior lower neck 2 (100) (50) 1 (50) 10. Coronal upper neck 0 (0) Coronal lower neck 0 (0) Posterior upper neck 1 (17) (17) 13. Posterior lower neck 0 (0) Total (% of discordant cases) 49 (43) 25 (51) 3 (6) 13 (27) 11 (22) 2 (4) 2 (4) 2 (4) Note. Data represent number of cases (%) with drainage to that location. involved an anterior lower neck melanoma that metastasized to the axilla (this patient has since had lung metastasis develop as well but is alive at last follow-up of 14 months) (Figure 2). One case (case 3) of melanoma of the posterior scalp had metastasis to an area beyond those predicted on either preoperative lymphoscintigraphy (levels II, V, and occipital) or clinical prediction (II V, occipital). Initially, this patient did have a positive SLN identified in level V of the neck, with an additional four positive nodes at level II on subsequent therapeutic neck dissection. However, Case Location of primary Predicted sites on lymphoscintigraphy Table 4. Cases of positive SLN. Areas not clinically predicted Location Pos SLN (no. of positive/ total SLN) Location positive nodes on ND (no. of positive/total LN) Location of recurrence or mets 1 1 Anterior scalp I IV, preauricular IV III (2/3) I (1/21) N/A 2 3 vertex II, occipital None Occipital (1/7) (0/no. of total not specified) Brain mets 3*# 3 Posterior scalp II, V occipital None V (1/2) II (4/70) Parotid, occipital 4 4 Preauricular II, preauricular None Parotid (1/1) Parotid (2/3) Lung mets 5 5 Ear I III, preauricular None II/III (2/8) (0/34) N/A 6* 6 Upper face Pre/postauricular Postauricular Postauricular (1/6) (0/9) N/A 7 6N Nose I IV IV II,III (4/4) II/III (4/26) Brain mets 8 6N Nose I V V I (1/5) (0/11) N/A 9 6N Nose I,II None I (2/9) Parotid (0/3), ND (0/23) N/A 10 6N Nose I,II None I (1/3) (0/4) N/A 11 7 Lower face II IV, preauricular IV Parotid (1/3) Parotid (pos N/A fibrofatty tissue, 0 LN) ND (0/4) 12* 9 Anterior Axilla Axilla Axilla (1/2) (0/25) Lung mets lower neck Coronal II,III,V None II/III (1/2) ND declined by pt II,III, Lung mets upper neck Posterior upper neck V, occipital None Occipital (1/4) (0/5) N/A Abbreviations: SLN, sentinel lymph node; ND, neck dissection; LN, lymph node. *Cases with positive nodes found outside of clinically predicted areas. #Cases in which positive nodes on therapeutic neck dissection (ND) or recurrence occurred at a site outside of areas predicted on preoperative lymphoscintigraphy. 252 Lymphatic Drainage Patterns in SLNB HEAD & NECK March 2006

5 FIGURE 1. Preoperative lymphoscintigraphy of a patient with a primary melanoma on the left anterolateral scalp. Anterior image of the head (left), acquired with transmission source behind the patient to assist in anatomic localization, demonstrates the injection site (superior) and drainage to the preauricular and postauricular areas down into the supraclavicular region. Left lateral image (right) shows in detail the multiple lymph channels and lymph nodes identified in the preauricular (PRA), postauricular (POA), cervical (C), and supraclavicular (SC) regions. 7 months later, the patient had occipital and unpredicted parotid recurrences and is still alive at month 10 of follow-up. Twelve cases had recurrences after negative SLNB (summarized in Table 5 and described previously 9 ). Eight cases had recurrences at the primary site. Two of the remaining four cases involved recurrences at sites clinically predicted but not seen on preoperative lymphoscintigraphy. In case 5, a primary melanoma of the ear recurred at a site more distal (level IV) to the sites seen on lymphoscintigraphy (II, III, postauricular). On therapeutic neck dissection for the recurrence, one of 35 positive nodes was found at level IV. The nasal facial melanoma in case 7 recurred in the parotid, whereas preoperative lymphoscintigraphy predicted drainage inferior to the ear (level II or the infra-auricular parotid nodes). On pathology, none of the lymph nodes found in the parotid region or neck contained melanoma, but the fibrofatty tissue of the parotid did. The remaining two cases were unsuccessful attempts at identifying a positive SLN. The SLN was not identified in case 3, and the patient s posterior scalp melanoma recurred in level V of the neck. In case 11, a melanoma of the lower face, three SLNs were identified, but none contained melanoma. A recurrence in level II of the neck was diagnosed and treated with an excisional biopsy at another facility. Completion neck dissection at our institution revealed 0 of 15 nodes containing melanoma. All four patients are alive without disease after an average of 17 months of follow-up (range, 9 30 months). DISCUSSION The combination of lymphoscintigraphy, Lymphazurin blue dye, and intraoperative gamma probe has enhanced the safety and reliability of the SLNB technique in providing prognostic information to patients with head and neck cutaneous melanoma. 7 9 However, preoperative lymphoscintigraphy often predicts drainage patterns that deviate from previously clinically predicted drainage patterns causing many to deem the head and neck lymphatic drainage complex, with many variations that may not be clinically significant. The 43% discordance between lymphoscintigraphy drainage patterns and clinically predicted drainage is within the range of previously described discordancy rates, including an earlier, but distinct, series at our institution (32% to 84%). 11,12,15,16 However, one could argue that many of these areas of discordancy are not actually clinically unexpected drainage sites. Fiftyseven percent of the discordant cases described (n = 28) had drainage to areas more inferiorly to clinically predicted drainage sites such as levels IV to VI of the neck and the axilla. Drainage to these distal sites has been described previously as an infrequent occurrence that has harbored metastatic melanoma In our series, only one of these 28 cases actually had melanoma in one of these distant sites (axilla). The postauricular region was involved in 51% of discordant cases (n = 25), with most cases seen involving primary melanoma of the scalp, in particular the posterior scalp, and the ear. Again, this drainage pattern has been described previously as containing metastatic melanoma and is known to drain the posterior portion of the parietal and mastoid FIGURE 2. Preoperative lymphoscintigraphy (anterior thorax without [left] and with [right] transmission source posterior to patient for anatomic localization) of a patient with a lower anterior neck primary melanoma (labeled Injection) with drainage to the right axilla (labeled LN). Patient is imaged with right arm above head. Lymphatic Drainage Patterns in SLNB HEAD & NECK March

6 Case Location of primary Table 5. Recurrences in cases of negative SLN biopsy. Predicted sites on lymphoscintigraphy Areas not clinically predicted Location Pos SLN (no. of positive/ total SLN) Location positive nodes on ND (no. of positive/total LN) Location of recurrence or mets 15 1 Anterior scalp II,III, pre/postauricular Postauricular (0/6) N/A Primary 16 2 Coronal scalp II,III None (0/5) N/A Primary 17 3 Posterior scalp V, occipital None (0/0) V (3/10) Neck (V) 18 3 Posterior scalp II,III, pre/postauricular Postauricular (0/4) N/A Primary 19# 3 Posterior scalp II,III, postauricular Postauricular (0/1) IV (1/35) Neck (IV) 20 5 Ear Postauricular Postauricular (0/4) N/A Primary 21# 5 Ear II None (0/6) Parotid (pos fibrofatty Parotid tissue, 0/2 LN) ND (0/27) 22 5 Ear II IV None (0/5) N/A Primary 23 6 Upper face II IV, preauricular None (0/1) N/A Primary 24 6 Upper face I III None (0/1) (0/9) Primary 25 6 Upper face II IV IV (0/3) Excision pos, Neck (II) ND (0/15) 26 6N Nose I,II None (0/1) N/A Primary Abbreviations: SLN, sentinel lymph node; ND, neck dissection; LN, lymph node. #Cases in which positive nodes on therapeutic neck dissection (ND) or recurrence occurred outside of areas predicted on preoperative lymphoscintigraphy. regions of the scalp, as well as the upper posterior portion of the ear Only one patient in our series was found to actually have melanoma in the postauricular region. Overall, two (14%) the 14 positive SLNB cases involved melanoma draining to sites outside of those clinically predicted. When taking into account the four additional cases that had regional metastasis develop after a negative SLNB, this percentage decreases to 11%, although this is close to the 13% (seven discordant positive nodes per 51 cases with involved lymph nodes) rate reported in the large series of 362 patients by dewilt et al. 16 Despite the low predictive value at these discordant sites, they still can harbor melanoma, and, at least until more conclusive evidence appears with longer follow-up in all series including this study, all sites predicted on preoperative lymphoscintigraphy still need to be explored. The interpretation of the lymphoscintigraphy images themselves relies on experienced nuclear medicine physicians with a strong knowledge of head and neck anatomy. An example is the case of an ear primary melanoma (case 7), which recurred in the parotid after a negative SLNB. Preoperative lymphoscintigraphy predicted infraauricular drainage, which could be interpreted as level II or drainage to the infra-auricular parotid nodes. Besides the ear, this region has been described as receiving drainage from the cheek, buccal mucosa, parotid, nose, upper eyelid, and the postauricular nodes. 17 This case underscores the importance of the interpretation of preoperative lymphoscintigraphy in guiding the search for the SLN. Despite a high success rate of identifying the SLN with this technique (97%), all of these patients need close follow-up, as illustrated by the four cases of regional recurrence. Two cases involved recurrences in sites not predicted on preoperative lymphoscintigraphy; one was more distal to the drainage sites predicted, and the other was in a site not predicted on lymphoscintigraphy (intraparotid). The other two cases were unsuccessful attempts at identifying the SLN predicted on lymphoscintigraphy. Lymph node tissue was harvested that did not contain melanoma, but as the recurrences indicate, the SLN with tumor was not removed at the time of SLNB. CONCLUSION On the basis of preoperative lymphoscintigraphy and the results of SLNB, head and neck cutaneous melanomas do have expected lymphatic drainage patterns despite perceived discordancy with previously clinically predicted drainage patterns that are based on standard neck dissection specimens. These discordant areas have unclear biological or clinical relevance, because few of the discordant sites actually contain metastatic disease. Despite this, they still can harbor melanoma, and, at least until more conclusive evidence appears with longer follow-up in all series including this study, all sites predicted on preoperative 254 Lymphatic Drainage Patterns in SLNB HEAD & NECK March 2006

7 lymphoscintigraphy still need to be explored. The four cases of recurrences underscore the importance of close follow-up for all patients regardless of SLNB result. REFERENCES 1. Pu LL, Wells KE, Cruse CW, Shons AR, Reintgen DS. Prevalence of additional positive lymph nodes in complete lymphadenectomy specimens after positive sentinel lymphadenectomy findings for early-stage melanoma of the head and neck. Plastic Reconstr Surg 2003;112: McMasters KM, Swetter SM. Current management of melanoma: benefits of surgical staging and adjuvant therapy. J Surg Oncol 2003;82: Rousseau DL Jr, Ross MI, Johnson MM, et al. Revised American Joint Committee on Cancer Staging Criteria accurately predict sentinel lymph node positivity in clinically node-negative melanoma patients. Ann Surg Oncol 2003;20: Balch CM, Soong SJ, Bartolucci AA, et al. Efficacy of an elective regional lymph node dissection of 1 to 4 mm thick melanomas for patients 60 years of age and younger. Ann Surg 1996;224: Cascinelli N, Morabito A, Santinami M, MacKie RM, Belli F. Intermediate or delayed dissection of regional nodes in patients with melanoma of the trunk: a randomized trial. Lancet 1998;351: O Brien CJ, Coates AS, Petersen-Schaefer K, et al. Experience with 998 cutaneous melanomas of the head and neck over 30 years. Am J Surg 1991;162: Morton DL, Wen DR, Wong JH, et al. Technical details of intraoperative lymphatic mapping for early stage melanoma. Arch Surg 1992;127: Schmalbach CE, Nussenbaum B, Rees RS, Schwartz J, Johnson TM, Bradford CR. Reliability of sentinel lymph node mapping with biopsy for head and neck cutaneous melanoma. Arch Otol Head Neck Surg 2003;129: Lin D, Kashani-Sabet M, Singer MI. The role of the head and neck surgeon in sentinel lymph node biopsy for cutaneous head and neck melanoma. Laryngoscope 2005; in press. 10. O Brien CJ, Petersen-Schaefer K, Ruark D, Coates AS, Menzie SJ, Harrison RI. Radical, modified and selective dissection for cutaneous malignant melanoma. Head Neck 1995;17: O Brien CJ, Uren RF, Thompson JF, et al. Prediction of potential metastatic sites in cutaneous head and neck melanoma using lymphoscintigraphy. Am J Surg 1995; 170: Leong SPL, Actem TA, Habib FA, et al. Discordancy between clinical predictions vs lymphoscintigraphic and intraoperative mapping of sentinel lymph node drainage of primary melanoma. Arch Dermatol 1999;135: Shah JP, Kraus DH, Dubner S, Sarkar S. Patterns of regional lymph node metastases from cutaneous melanomas of the head and neck. Am J Surg 1991;162: Pathak I, O Brien CJ, Petersen-Schaeffer K, et al. Do nodal metastases from cutaneous melanoma of the head and neck follow a clinically predictable pattern? Head Neck 2001;23: Wells KE, Cruse CW, Daniels S, Berman C, Norman J, Reintgen DS. The use of lymphoscintigraphy in melanoma of the head and neck. Plast Reconstr Surg 1994;93: dewilt JHW, Thompson JF, Uren RF, et al. Correlation between preoperative lymphoscintigraphy and metastatic nodal disease sites in 362 patients with cutaneous melanomas of the head and neck. Ann Surg 2004;239: Haagensen CD, Feind CR, Hertner FC, Slanetz CA Jr, Weinberg JA. The lymphatics in cancer. Philadelphia: W.B. Saunders Company; Lymphatic Drainage Patterns in SLNB HEAD & NECK March