preoperative ultrasonographic identification of the sentinel lymph node in patients with malignant...

Preoperative Ultrasonographic Identification of theSentinel Lymph Node in Patients with MalignantMelanoma

Birgit Kahle, M.D.1

Johannes Hoffend, M.D.2

Jorg Wacker, M.D.1

Wolfgang Hartschuh, M.D.1

1 Department of Dermatology, Heidelberg Univer-sity, Heidelberg, Germany.

2 Department of Radiology, Department of NuclearMedicine, Heidelberg University, Heidelberg, Ger-many.

See editorial on pages 1821–3, this issue.

Address for reprints: Birgit Kahle, M.D., Depart-ment of Dermatology, University of Heidelberg,Vo�str.2, D-69115 Heidelberg, Germany; Fax:(011) 49 6221 56-5945; E-mail: [email protected]

Received February 19, 2002; revision receivedOctober 24, 2002; accepted November 8, 2002.

BACKGROUND. Dissection of the “sentinel lymph node” (SLN) as identified by

lymphoscintigraphy is becoming increasingly important in the treatment of pa-

tients with malignant melanoma. The purpose of the current study was to deter-

mine whether the SLN also could be identified by ultrasound.

METHODS. Sixty-seven patients with malignant melanoma (40 females and 27

males, with an average age of 48.8 years) in whom extirpation of the SLN was

indicated underwent ultrasonography of the regional lymph nodes prior to preop-

erative lymphoscintigraphy. The location of the melanoma was the legs in 30

patients, the arms in 14 patients, and the trunk in 23 patients. During regional

ultrasonography, the location of the lymph nodes that differed in the cortex/

medulla ratio from the surrounding lymph nodes was marked on the skin corre-

sponding to the planes of insonation (M1) when the probe was held vertically to

the skin surface. After lymphoscintigraphy using technetium-99m, the position of

a gamma probe at which the highest count rate vertical to the skin surface was

recorded also was marked (M2).

RESULTS. In the inguinal region, the agreement between M1 and M2 was found to

be 100% (40 of 40 SLNs) and was 72.5% in the axilla (29 of 40 SLNs). In patients with

melanomas located on the leg, the location of M1 and M2 agreed in 97% of cases

(36 of 37 lymph nodes in 30 patients); in patients with melanomas located on the

arms, the agreement was 76% (13 of 17 lymph nodes in 14 patients) and in patients

with melanomas located on the trunk, the agreement was 75% (21 of 28 lymph

nodes in 23 patients). The position documented by ultrasound relative to the

neighboring structures of the SLN was confirmed intraoperatively in all cases.

CONCLUSIONS. The results of the current study indicate that the SLN in patients

with melanoma located on the limbs, especially the legs, are characterized by a

specific sonomorphologic pattern. Preoperative sonography might constitute an

important addition to lymphoscintigraphy in the planning of SLN biopsy. Cancer

2003;97:1947–54. © 2003 American Cancer Society.

DOI 10.1002/cncr.11261

KEYWORDS: malignant melanoma, sentinel lymph node (SLN), ultrasonography,lymphoscintigraphy.

Sentinel lymph node (SLN) biopsy has assumed an important rolein the surgical treatment of malignant melanoma.1,2 The method

first was devised in 1977 by Holmes et al.,3 who described regionallydraining lymph nodes marked with radioactive colloidal gold in pa-tients with melanoma, and by Cabanas,4 who to our knowledge wasthe first to use the term “sentinel [lymph] node” in cases of penilecarcinoma. Morton et al.5,6 defined the SLN as the first lymph nodethat receives lymphatic drainage of the tumor. In systematic studies,

1947

© 2003 American Cancer Society

the authors investigated the technique as well as theclinical usefulness of SLN biopsy.5,6

The actual status of regional lymph nodes at thetime of surgery for melanoma has been reported tohave high prognostic value5 with regard to their clin-ical significance in the progression of melanoma.1,7,8

Assuming that the SLN is part of the drainage pathwayto additional regional lymph nodes, it is ascribed animportant filter function for potential metastases. TheSLN is considered representative of the respective re-gional lymph node group.

The mapping of the SLN requires appropriate lo-calization. Identification by lymphoscintigraphy withradiolabeled colloids currently is the most widely usedmethod.2,6,9 Intraoperative mapping is possible usinga probe optimized for the technetium-99m (Tc-99m)label. It occasionally can be helpful to stain the SLNusing peritumoral cutaneous injection of Patent BlueV to improve its identification during surgery.

The current study was conducted to evaluatewhether the SLN also can be mapped by ultrasound,whether this technique can identify the reference toneighboring structures clearly, and whether ultra-sonography of the SLN is of clinical value in patientswith malignant melanoma.

MATERIALS AND METHODSPatientsSixty-seven patients (40 females and 27 males, with anaverage age of 48.8 years) with malignant melanomathat was located on the trunk or the extremities wereenrolled after informed consent was obtained. All pa-tients had tumors with a Breslow thickness of � 1.0mm (range, 1.08 –5.5 mm) and a Clark level � III;therefore, wide excision combined with SLN biopsywas indicated. In 32 patients, SLN biopsy and widelocal excision followed as a second procedure afterprimary excision of the melanoma. Patients with mel-anoma of the head or neck were not included.

In 30 patients, the primary melanoma was situ-ated on the lower extremity with the SLN located inthe inguinal area. In 14 patients, the melanoma wasfound on the arms and the SLN was in the axilla. In 23patients, the tumor was situated on the trunk withmainly axillary lymphatic drainage (16 cases in 1 of theaxilla basins and 2 cases in both axillary basins). Intwo cases the pathway was to the ipsilateral axilla andinguinal area, in two cases the drainage was inguinal,and in one case it was nuchal.

Investigational ConditionsUltrasonography was performed using the color-coded Doppler Apogee 800 ultrasound system (Ad-vanced Technology Laboratories, Solingen, Germany),

with a 7.5-megahertz (MHz) and an 11-MHz lineartransducer. At these probe frequencies, the axial sep-aration was 0.2 mm or 0.12 mm, respectively; theaxillary and inguinal lymph nodes could be visualizedfrom a size of 2–3 mm upward. Pathological changescan be assumed if the sonographic image demon-strates lymph nodes measuring � 3– 4 mm.10

The investigation always was performed with thepatient in the supine position, with the leg in abduc-tion and in external rotation when visualizing the in-guinal lymph nodes, and with the arm elevated andthe hand placed under the head for the axillary lymphnodes. Care was taken to ensure that the position ofthe patient during sonography and lymphoscintigra-phy corresponded to the positioning during surgery.

Course of the InvestigationIn a first step, 1 day before lymphoscintigraphy andsurgery were performed, all lymph nodes within theentire basin were scanned by ultrasound. Asymmetriclymph nodes were conspicuous. The size and the po-sition of these lymph nodes relative to the skin surfaceand anatomic landmarks were documented. For theinguinal region these structures were: the commonfemoral vein, the great saphenous vein, and the com-mon and superficial femoral artery. For the axilla theanatomic landmarks were: the major pectoral muscle,the thoracodorsal artery, and the axillary vein andartery. To avoid a shifting of the transducer whilemarking the skin, the physician performing the ultra-sound (B.K.) positioned the probe perpendicular, con-trolling the suspicious SLN in real-time mode while anassistant (J.W.) marked the skin. The ultrasoundplanes of the maximal longitudinal and cross-sec-tional dimensions of the conspicuous lymph nodeswere marked on the skin (Fig.1). The intersection ofthese axes was designated M1.

For lymphoscintigraphy, 40 –50 megabecquerelsof Tc-99m colloid (Nanocoll�; Sorin Biomedica, Salug-gia, Italy) in a volume of 0.5 mL was injected intrad-ermally in 4 depots of 0.15 mL each around the mel-anoma or the biopsy site. The patient then waspositioned as described earlier (investigational condi-tions). Dynamic images were acquired for the first 10minutes. Serial static views were acquired until 1 h p.i.in a matrix of 256 � 256 with a double-headed gammacamera with a large field of view (ECAM; Siemens,Berlin, Germany) fitted with a high resolution collima-tor. Care was taken to image not only the greaterlymphatic basins in the inguinal area and the axillabut also the lesser lymphatic basins of the cubital andpopliteal fossae and possible lymph nodes along thedrainage paths on the trunk. In cases of multipledrainage (especially in cases of melanoma of the

1948 CANCER April 15, 2003 / Volume 97 / Number 8

trunk), multiple projections were acquired to follow alldrainage pathways. On the serial images the SLN wasdefined as the first focus of activity in the respectivedrainage pathway. As part of the standard procedure,the SLN or SLNs were localized roughly by scintigra-phy; the exact location of the respective lymph nodesin relation to the skin surface was determined by usinga handheld gamma probe (CXS; Crystal, Berlin, Ger-many) with a lower threshold (120 kiloelectron volt)window fixed at 20%. An identical probe was usedintraoperatively. The nuclear medicine physician(J.H.), who was unaware of the true meaning of theskin indications, marked the point on the skin (M2)(Fig. 2) at which the gamma probe recorded the high-est count rate when the instrument was held verticallyto the skin surface. The nuclear medicine physician(J.H.) and the 2 surgeons (B.K. and W.H.) who tookpart in the current study had established the SLNbiopsy as a routine procedure 2 years before preoper-ative ultrasound examination of the SLN was initiated.An essential part of the introduction of the gammaprobe was the effort to always keep the probe perpen-dicular to the skin surface because this positioning ofthe probe was believed to provide the most consistentand comparable interindividual results with regard tolocalization of hot spots.

Before surgery, ultrasonography of the basin wasrepeated; the size, shape, and position of the SLN wereregistered and the markers M1 and M2 were com-pared (Fig. 2) and documented. Local anesthesia (tu-mescence solution containing 50 mL of prilocain in500 mL of sodium chloride) then was infused aroundthe melanoma/site of previous melanoma removal

and in the regional lymph basin (axilla or inguinalregion). Approximately 5–10 minutes before surgerywas initiated, 1–2 mL of Patent Blue V (Patent Blue2.5%; Guerwe GmbH, Sulzbach, Germany) was in-jected strictly intracutaneously around the tumor orthe site of the primary excision. After application ofthe anesthesia and Patent Blue V, the patients werepositioned on the surgery table as described previ-ously for SLN biopsy.

Intraoperatively, the SLN was dissected using thehandheld gamma probe. If after removal of the SLNonly background activity was recorded in the surgerysite, the excision of the SLN was considered complete.The removed SLN then was (ex vivo) cut in two alongthe longitudinal axes for histologic (hematoxylin andeosin [H & E] staining) and immunohistologic exami-nation (HMB 45 and S-100 staining) of multiple sec-tions per half. Before being sent to the laboratory, thetwo halves were measured and photographed for doc-umentation (Fig. 3).

RESULTSGeneral ResultsCareful sonographic measurements of the entirety ofeach respective lymphatic basin revealed a distinctiveasymmetry between the cortex and medulla in onlyone or two lymph nodes compared with all the otherlymph nodes of that basin (Fig. 4). These lymph nodeshad a localized thickening of the cortex reminiscent ofa cap (Figs. 4, 5). To quantitate this visual impressionof asymmetry, the ratio between the cortex and me-dulla was calculated on either side of a vertical linethrough the hilus (Fig. 5).

Lymph nodes with ratio of � 1.2 between the

FIGURE 1. Positioning of the ultrasound probe on the skin in the left inguinal

area while the patient was in the supine position. The planes of insonation of

the sentinel lymph node are marked in green. The mark M1 (green axes)

represents the point of intersection of the planes of insonation by sonography.

The upper left corner was oriented toward the head of the patient; the lower left

corner points to the medial left thigh.

FIGURE 2. The red mark (M2) represents the point with the highest count

rate of the lymphoscintigraphy. M2 corresponds with the intersection of the

green axes (M1). The upper border of the image was oriented toward the head

of the patient; the right border points to the lateral left thigh.

Ultrasonography of the Sentinel Lymph Node/Kahle et al. 1949

cortex and medulla as described earlier were regardedas the SLN. Inspection of the SLNs after extirpationrevealed an increase of the cortex in a peripheral di-rection in the longitudinal dimension, correspondingto the location of the sonographic “cap,” and alsocorresponding to the point of maximum Patent Blue Vstaining in 58 cases (Fig. 3). Ex vivo count rates mea-

sured with the gamma probe always were found to behighest in the region of the “cap.” Longitudinal andcross-sectional dimensions of the lymph nodes mea-sured by preoperative sonography corresponded tothose found macroscopically after lymph node re-moval.

In 67 melanomas, 70 conspicuous lymph nodeswere detected sonographically and 82 SLNs identifiedby lymphoscintigraphy. All marks made during sonog-raphy (M1) corresponded directly to those made dur-ing scintigraphy (M2). The points of intersection of thegreen axes used to locate the lymph nodes detected byultrasound corresponded to the scintigraphic markers(Fig.2).

After lymphoscintigraphy but before local anes-thesia was administered, the ultrasound scan was re-peated. Only in those lymph nodes considered SLN bysonomorphologic criteria had the cortex become lesshypoechoic in comparison with the initial examina-tion. The demarcation from the surrounding tissuewas no longer as clear as in the first investigation.

The number of SLNs per patient diagnosed byscintigraphy demonstrated no dependence on respec-tive tumor thickness or regression zones present in themelanoma or the subsequent detection of distant me-tastases.

Detailed ResultsMelanoma of the legsIn 29 of 30 patients with melanoma located on thelegs, the lymphatic pathway drained in the inguinalarea. In all these cases the SLNs were detected sono-graphically. In six patients, two SLNs were found bothby ultrasound and by lymphoscintigraphy. In 29 pa-tients, the number of SLNs diagnosed by sonography

FIGURE 3. Longitudinal section through the sentinel lymph node shown in

FIGURE 1. Staining of the pole by Patent Blue V, which corresponds to the

“cap,” was marked with an arrow.

FIGURE 4. A sentinel lymph node in the inguinal area of a patient with

malignant melanoma with a Breslow index of 1.8 mm and and Clark level IV

located on the left abdomen. The left half of the picture is in longitudinal

section, the right half is in cross-section. The cap-like cortical thickening is

marked with an arrow. The dimensions of the lymph node were 9.45 mm

� 8.19 mm (a � b) in the longitudinal section and 8.25 mm � 6.31 mm (c

� d) in the cross-section.

FIGURE 5. Scheme of the ratio cortex/medulla in the sentinel lymph node

(SLN) in contrast to the symmetric ratio in so-called reactive lymph nodes. In

the SLN, the quotient of the longitudinal distances from the middle of the

medulla to the border of the medulla and cortex, a1/b1 divided through the

equivocal quotient a2/b2, is higher than 1.2. In reactive lymph nodes, this ratio

is approximately 1.0.


was the same as that diagnosed by scintigraphy (n� 36). In one patient with melanoma of the sole in thecalcaneal region the SLN was diagnosed scintigraphi-cally in the popliteal fossa. No suspicious lymph nodeswere found in the inguinal area of this patient; thepopliteal region was not screened routinely with ul-trasound. The mean dimension of the SLN in theinguinal area was 7.5 mm � 3 mm and the SLNs werefound to be situated 16 mm � 4 mm below the skinsurface.

Melanoma of the armsAll 14 melanomas located on the arms drained into theipsilateral axilla. In nine patients one SLN and in twopatients two SLNs were detected by both ultrasoundand scintigraphy. The cutaneous markers M1 and M2corresponded in these cases. In three patients, accu-rate sonographic detection of the SLN was not possi-ble because of significant obesity but lymphoscintig-raphy detected four SLNs. In two of the three obesepatients the SLN could not be found intraoperativelybecause of excessive adiposity of the axilla. The cubitalfossa was not assessed routinely by sonography. Themean dimension of the SLN in the axilla was 8.9 mm� 3 mm and the SLNs were situated 20.5 mm � 4.7mm below the skin surface.

Melanoma of the trunkIn 23 patients with melanoma of the trunk, 21 SLNswere identified on ultrasound and 27 were identifiedby lymphoscintigraphy. The cutaneous markers M1and M2 were found to correspond in these 21 cases.Sixteen of the 23 cases of melanoma of the trunkdrained into 1 SLN in 1 axilla. Only 11 of these caseswere identified by ultrasound. Two melanomasdrained into both axillae. Three of the four SLNs weredetected by both ultrasound and scintigraphy, andone SLN was identified by scintigraphy only. Two pa-tients with melanomas of the trunk had SLNs in oneaxilla and the ipsilateral inguinal area. Four of fiveSLNs were found by both ultrasound and scintigraphy,and one SLN was found by scintigraphy only.

Two tumors drained only into the inguinal area, inwhich all SLNs were identified sonographically.

In one patient, the lymphatic drainage was intothe neck. This region was not routinely examined byultrasound; the axillae demonstrated no suspiciouslymph nodes.

HistologyIn 11 patients, there was histologic and immunohis-tologic evidence of metastasis of the SLN. Intraopera-tively, these lymph nodes had demonstrated no ab-normalities in size or shape; however, one of these

lymph nodes was firm on palpation. The capsule hadnot been penetrated in either case. In one case themetastasis was localized in the “cap.”

Patent blue v stainingPreoperative peritumoral intracutaneous injection ofPatent Blue V stained 58 SLNs. In these cases, PatentBlue V was found only in the periphery (i.e., the pole ofthe lymph node pointing toward the tumor). In the exvivo longitudinal section, the Patent Blue V accumu-lated mainly in that part of the SLN with the highestradioactive count rate, which corresponded to the hy-poechoic cap noted on ultrasound imaging (Fig. 3).

DISCUSSIONSLN biopsy, which is reportedly less invasive than anelective lymphadenectomy,11 is recommended for pa-tients with malignant melanoma with a tumor thick-ness � 1.0 mm.12,13

In our institution, sonography of the lymphaticdrainage is part of the staging of malignant melanoma.During these routine sonographies, we observed aparticular morphologic pattern that was present inonly one or two lymph nodes in the entire basin. In afirst step we attempted to characterize the specialsonomorphology, and in a second step we tried toestablish whether these lymph nodes corresponded toSLN as characterized by lymphoscintigraphy.

The hallmark of the lymph nodes presumed to beSLNs in the current study was their conspicuousasymmetry. This asymmetry, which can best be ex-pressed by variations in the ratio between the cortexand medulla as described earlier, is due to a localizedthickening of the cortex at the peripheral pole thatreminds one of a “cap” (Figs. 4, 5). Corresponding tothe cortical thickening, a localized staining of thelymph node cortex was found during surgery by priorintracutaneous injection of Patent Blue V in 58 cases(Fig. 3). One explanation could be that the cap-likecortical thickening of the SLN diagnosed by sonogra-phy corresponds to the region in which the melano-ma-specific afferent lymph vessel joins the lymphnode.

The time interval between excision of the mela-noma and SLN dissection most likely is unimportantin terms of the extent of the asymmetrical corticalthickening. In 35 of 67 patients in the current study,the primary tumor had not been removed at the timeof sonography and scintigraphy. The SLN of thesepatients demonstrated the “cap” phenomenon to thesame extent as those of the patients who had under-gone melanoma removal 6 – 8 days earlier. Differenttumor locations and distances between the SLN and


the primary tumor likewise appear to have no influ-ence on the shape and size of the SLN.

Sonography performed as part of melanoma fol-low-up often detects so-called reactive lymph nodesthat are, however, not necessarily suspicious. Theselymph nodes with reactive changes demonstrate, inaddition to a marked enlargement, a symmetricallythickened cortex that, through the abundance of cells,appears nearly anechoic and therefore contrasts wellwith the echo-rich medulla. This structure, describedas resembling a cockade, differs markedly from the“cap” phenomenon and is typical of reactive lymphnodes. Moreover, reactive lymph nodes are symmet-rical.10

In contrast, a considerable asymmetric thickeningof the cortex and additional morphologic patternssuch as round, anechoic areas in the lymph nodes; adistinct vascularization pattern; and occasionally apenetrated capsule are interpreted as evidence of me-tastasis.1,4,5 Apart from the typical “cap” phenome-non, the SLN we identified with sonography demon-strated no further abnormal morphology. The centralvascular architecture was retained. Histology and im-munohistochemistry of the SLNs in the current studydemonstrated metastatic disease (micrometastasis) in11 of 82 lymph nodes (13.4%).

To our knowledge, there is no common markerthat reliably labels a lymphatic node for both sonog-raphy and radio-guided detection. Therefore, it wasnot possible to prove directly the identity of sono-graphic and scintigraphic findings. To ensure as muchas possible that the lymph node identified by sonog-raphy was indeed the SLN as identified by scintigra-phy and the gamma probe we adhered to the followingprinciples:

1. The nuclear medicine physician was unaware ofthe meaning of the skin marks when he saw thepatient for lymphoscintigraphy. Moreover, the M1ultrasound marks were applied several centime-ters away from the probe-guided mark M2.

2. Because the gamma probe provides the best signalwhen placed vertically on the skin surface anddirectly above the SLN, the ultrasound examina-tion also sought to position the ultrasound probelikewise vertically to the skin when the SLN wasmarked.

3. The location of a lymph node with regard to theneighboring anatomic landmarks varies with theposition the patient assumes during a procedure.For the four procedures involved (sonography,scintigraphy, probe-guided detection, and sur-gery), we always positioned the patient in thesame way. This was particularly important for sur-

gery of the axilla, during which the supine patientwas asked to elevate the arm and place the handbelow the head.

4. To identify the conspicuous lymph node in a man-ner independent of the indications on the skin, theposition of a particular lymph node in relation tothe surrounding surgical anatomy and in relationto other surrounding lymph nodes was recordedmeticulously.

The anatomic situation recorded preoperativelyfor the SLN identified by sonography coincided ineach case with the anatomic findings when the SLNidentified by scintigraphy and the gamma probe washarvested. However, in a proportion of our patients wecannot exclude a possible bias of the surgeon whoperformed the SLN biopsies. In approximately 33% ofpatients, ultrasound was performed by the same sur-geon (B.K.) who later performed the SLN biopsy. In theremaining 67% of the patients, the surgeon who har-vested the SLN (W.H.) was unaware of the ultrasoundfindings.

At biopsy, the distance of the SLN from the skinsurface was roughly equal (because of tumescenceanesthesia) to that determined preoperatively. Noother lymph node was detected by ultrasound andduring surgery between the skin surface and the pre-sumed SLN. Vertical stacking of lymph nodes there-fore can be excluded as a source of error.

The patients in the current study were included inthe regular follow-up ultrasound examinations. Thelymph nodes remaining after SLN biopsy werescanned at intervals of s6 months. The remaininglymph nodes did not demonstrate any conspicuousasymmetry between the cortex and medulla duringfollow-up.

Our initial observations regarding lymph nodemorphology were made in the inguinal area. Here, thetissue covering the lymph nodes was between 10 –20mm wide in the current study patients, and the pre-sumed SLN with a mean dimension of 7 mm and theanatomic landmarks were readily discernible. Giventhat M1 and M2 coincided with a disagreement be-tween both probes is only possible if the probes aretilted. The probes have to be tilted by at least 12degrees to shift the target volume 3 mm sideways in adepth of 10 –20 mm from the skin. This means that theprobe has to be tilted visibly to miss a SLN that mea-sures an average of 7 mm and usually is separatedfrom neighboring lymph nodes by 1–2 mm.

An additional hint are the changes in lymph nodeappearance after injection of the radioactive colloidthat is transported by the lymphatics. When after lym-phoscintigraphy the lymph node that appeared as the


SLN by ultrasound was reexamined, the cortex of onlythis lymph node but none of the neighboring lymphnodes had become less echogenic.

In each patient in the current study, lymphoscin-tigraphy was followed by resection of the primarytumor and/or wide local excision in addition to SLNbiopsy. Further changes in the ultrasound morphol-ogy of the presumed SLN because of injection of alocal anaesthetic around the primary tumor/site ofwide local excision or into the lymphatic basin cannotbe excluded. Moreover, it is important to note that theultrasound observations reported in the current studyall were made preoperatively.

In addition, all SLNs identified by ultrasound werefound by scintigraphy but not vice versa. Therefore,we currently do not recommend ultrasound as themeans of localizing the SLN intraoperatively. How-ever, taking the anatomic and functional informationtogether, we believethat the asymmetric lymph nodedemonstrating the “cap” phenomenon indeed corre-sponds with the SLN found by standard lymphoscin-tigraphy and a gamma probe.

The best correspondence between SLNs identifiedultrasonographically and scintigraphically was ob-served in the inguinal area (Table 1). In all melanomasdraining into the inguinal area, including those of thetrunk, the SLN was detected by both ultrasound andlymphoscintigraphy (Table 2). In 1 of the 37 melano-mas of the lower limb, the tumor was located in thedrainage region of the small saphenous vein, and theSLN was found in the popliteal fossa by scintigraphy.Because SLNs are very rarely found in the popliteal orcubital fossae, both regions were not examined rou-tinely by ultrasound, and thus the one SLN in thepopliteal fossa was not detected. In the remaining 36

of 37 melanomas of the lower extremity, the SLNswere situated in the inguinal area below the inguinalligament and were detected by ultrasound.

In the axilla, the agreement between ultrasoundand lymphoscintigraphy was 72.5%, which was lowerthan that noted in the inguinal area. One reason forthe less favorable results in the axilla was obesity; theobesity noted in three patients resulted in SLN biopsyin the axilla being unsuccessful and having to be ter-minated prematurely.

Our initial experience in the axilla was comprisedof not only melanomas of the arms but also fourmelanomas located over the inferior margin of thescapula. From the position of the melanomas we hadexpected lymphatic drainage only to the ipsilateralaxilla. Unexpectedly, in each of these patients lym-phoscintigraphy found a SLN in both the contralateraland ipsilateral axillae. Drainage pathways on the trunkare known to be complex and unpredictable.14 –17 Inthe patients that followed, ultrasound in truncal mel-anoma was extended to both axillae as well as bothinguinal areas. In an additional patient with mela-noma of the shoulder, ultrasound correctly identifiedone SLN in the axilla but lymphoscintigraphy detecteda second SLN in the neck.

At the current time, lymph node sonography hasan established role in the diagnosis and follow-up ofpatients with malignant melanoma. In the hands of anexperienced investigator, the method achieves a highsensitivity and specificity.18 –20 In our opinion, preop-erative imaging of the SLN represents an additional,new indication for lymph node ultrasonography inmalignant melanoma. The surgeon thereby obtainsimportant information regarding the position of theSLN in relation to its neighboring structures and can

TABLE 1Detected SLNs per Melanoma

Melanomas and position Basin Detected by sonography M1 Detected by scintigraphy M2 M1 � M2

30 melanomas of the lowerlimbs

29 � inguinal1 � popliteal

36 SLN 37 SLN 36 of 37, 97% Popliteal SLN notidentified by US

14 melanomas of theupper limbs

14 � axillar 13 SLN 17 SLN 13 of 17, 76%

23 total 21 SLN 28 SLN 21 of 28, 75%23 melanomas of the trunk 16 � 1 axilla 11 SLN 16 SLN 11 of 16, 69%

2 � both axilla 3 SLN 4 SLN 3 of 4, 75%2 � axilla plus inguinal 4 SLN 5 SLN 3 of 5, 60%1 � inguinal 1 SLN 1 SLN 1 of 1, 100%1 � both inguinal 2 SLN 2 SLN 2 of 2, 100%1 � nuchal – – –

Total of 67 melanomas 70 sono 82 scinti 70 of 82, 85.4%

M1: intersection of the axes of the ultrasound planes of maximal longitude and cross-sectional dimensions of the conspicuous lymph nodes; M2: the point on the skin at which the gamma probe recorded the highest

count rate when the instrument was held vertically to the skin surface; SLN: sentinel lymph nodes; US: ultrasound; Sono: sonography; scinti: scintigraphy.


prepare for surgery and plan the procedure accord-ingly. In some cases of SLN extirpation, the surgicalapproach is anatomically easier by when the skin in-cision is made away from the approach indicated bythe gamma signal (e.g., when the SLN lies under thegreat pectoral muscle or superior to the inguinal liga-ment). In the axilla, it is helpful to know the anatomicposition of the SLN, especially its depth, to decidewhether the SLN can be biopsied with regional anes-thesia or whether general anesthesia is needed. In theideal case, the surgeon is present during the “sentinelultrasonography” or performs it himself or herself.

In our opinion, the results of the current studydemonstrate that the SLN shows a typical sonomor-phologic pattern. Preoperative knowledge of the posi-tion of the SLN in relation to critical anatomical struc-tures may impact the surgical approach and strategy.

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TABLE 2Percentage of Identified SLNs by Ultrasound per Basin

Regional basin

Identified SLNby ultrasound,M1

Identified SLNby scintigraphy,M2 M1 � M2

Groin 41 41 41 of 41, 100%Axilla 29 40 29 of 40, 72.5%Neck Not examined 1 No correlationPopliteal fossa Not examined 1 No correlation

SLN: sentinel lymph node; M1: intersection of the axes of the ultrasound planes of maximal longitude

and cross-sectional dimensions of the conspicuous lymph nodes; M2: the point on the skin at which the

gamma probe recorded the highest count rate when the instrument was held vertically to the skin

surface.


preoperative ultrasonographic identification of the sentinel lymph node in patients with malignant...

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