Summary

Background

Inappropriate skin incisions can make sentinel lymph node dissection difficult. A knowledge of the most common locations of the hotspot in the axilla helps in planning the incision. This information also helps to locate the lymph node preoperatively by ultrasound. The aim of this prospective study was to determine the most common location of the sentinel lymph node in the axilla.

Methods

From January 2006 to December 2010, 974 consecutive patients who underwent sentinel lymph node dissection guided by 99mTc–sulfur colloid were included and the position of the hotspot in the axilla was recorded prospectively. The location of the hottest spot on the skin of the axilla was categorized into seven areas divided by five landmarks.

Results

In 98.4% of our patients, the hotspot detected on the axilla skin before sentinel lymph node dissection was located in the area demarcated by the four landmarks of the hairline, a line tangential to and 2 cm below the center of the hairline, the lateral border of the pectoralis major muscle, and the mid-axillary line.

Conclusion

The area between these four landmarks is the most frequent location of the sentinel lymph node identified using the radioisotope method. We suggest that this area should be carefully evaluated preoperatively by ultrasound for appropriate surgical planning. A skin incision in this area is also recommended when sentinel lymph node dissection is guided by blue dye.

Keywords

breast cancer;sentinel lymph nodes;sentinel lymph node dissection

1. Introduction

Axillary lymph node status is the most important prognostic factor in patients with breast cancer. Sentinel lymph node dissection (SLND) is now replacing axillary lymph node dissection for the determination of axillary lymph node status in patients with breast cancer without palpable axillary lymph nodes.1; 2; 3 ;  4 SLND can be guided by radioisotopes or by blue dye, or both. When SLND is guided by radioisotope, the incision can be made over the hottest spot in the axilla; when it is guided by blue dye, the incision is usually made about 1–2 cm below the hairline in the axilla.5 ;  6 Because an inappropriate incision can make intraoperative lymphatic mapping difficult, especially when using the blue dye method,5 a knowledge of the most common location of the hotspot in the axilla during radioisotope-guided SLND should not only help to plan the incision for SLND guided by blue dye, but also help to locate the lymph node preoperatively by ultrasound.

The aim of this prospective study was to determine the most common location of the sentinel lymph node (SLN) in the axilla as shown by the hottest spot on the skin in the axilla after periareolar injection of radioactive colloid.

2. Methods

From January 2006 to December 2010, all consecutive patients who underwent SLND performed by the same surgeon (C.-S.H.) in the National Taiwan University Hospital were included in this study. Patients with previous neoadjuvant chemotherapy were excluded. The SLND information, including the position of the hotspot in the axilla, was recorded prospectively.

The SLN biopsy procedure was guided by a 99mTc–sulfur colloid with intradermal periareolar injection in the quadrant where the tumor was located.7 Two protocols for radioactive colloid injection were used. In the 2-day protocol, 2 mCi of filtered (0.22 μm) 99mTc–sulfur colloid were injected in the afternoon 1 day before the operation. In the 1-day protocol, 1 mCi of filtered 99mTc–sulfur colloid was injected on the morning of the day of the operation.

The patients were all placed in a saluting position during surgery (i.e. arm abduction from the chest wall about 105°, flexion 15°, and elbow flexion) with a soft pad to elevate the arm (Fig. 1). In this position, the axillary area was divided into seven areas divided by five landmarks, which were labeled A to E. Landmark A was the lowest part of the hair-bearing area (hairline); B was the line drawn tangential to, and 2 cm below, the center of landmark A; C was the mid-axillary line which crosses the center point of the hairline; D was the lateral edge of the pectoralis major muscle; and E was the lateral edge of the latissimus dorsi muscle (Fig. 2). Location 1 was the area surrounded by A, B, C, and D. Location 2 indicated the point of intersection of B and C. Location 3 was the point of intersection of A and C. Location 4 was the area surrounded by A, B, C, and E. Location 5 was the area between C, E and the area above line A. Location 6 was the point on line C, 2 cm away from location 3 cephalically. Location 7 was the area between C, D and the area above line A (Fig. 3).


Position of the patient with arm abduction from the chest wall of around 105°, ...


Figure 1.

Position of the patient with arm abduction from the chest wall of around 105°, 15° flexion, and elbow flexion, with a soft pad to elevate the arm. The red cross denotes the location of the sentinel lymph node detected preoperatively by gamma probe; the blue circle shows the sentinel lymph node detected by radioisotope scintigraphy. The three black lines indicate the lateral edge of the pectoralis major muscle, the hairline, and the lateral edge of the latissimus dorsi muscle (from upper to lower, respectively).


Schematic diagram showing the five landmarks on the skin of the axilla.


Figure 2.

Schematic diagram showing the five landmarks on the skin of the axilla.


The seven areas demarcated by the five landmarks shown in Figure 2.


Figure 3.

The seven areas demarcated by the five landmarks shown in Figure 2.

Before incision, the position of the hottest spot on the skin of the axilla was detected using a handheld gamma probe (Navigator GPS, US Surgical, Tyco Healthcare Group, Norwalk, CT, USA) and assigned to one of these seven areas (Fig. 3). The position was marked on the skin of the axilla and the incision was made over the mark.

3. Results

During the study period, 1044 consecutive patients underwent an SLN biopsy procedure in our institution. Of these, SLND was unsuccessful in 70 patients, who were then excluded from the study. The remaining 974 patients who underwent a successful SLN biopsy procedure were included in this study.

The hottest node was detected at location 1 in 356 patients (36.6%), location 2 in 531 patients (54.5%), location 3 in 71 patients (7.3%), location 4 in one patient (0.1%), location 6 in one patient (0.1%), and location 7 in 14 patients (1.4%). No patient had the hottest spot at location 5. Overall, in 958 patients (98.4%), the hottest spot was at location 1, 2, or 3.

4. Discussion

In 98.4% of patients, the hottest spot detected on the axilla skin before SLND, identified by intradermal periareolar injection of radioisotope, was located in the area demarcated by the hairline, a line tangential to and 2 cm below the center of the hairline, the lateral border of the pectoralis major muscle, and the mid-axillary line. This information will be helpful in planning the incision for SLND guided by blue dye, as inappropriate incisions can make intraoperative lymphatic mapping difficult.

Giuliano et al8 first introduced SLND in patients with breast cancer in 1994 using the blue dye method and suggested a transverse incision just below the hair-bearing region of the axilla. Later, Dauway et al5 recommended making the incision 1 cm below the hair-bearing area. A blue node may be difficult to identify when it is covered by a substantial layer of fat9 and a knowledge of the most frequent location of the hottest spot on the axilla skin, indicating the location of the SLN, should help surgeons plan the incision for SLND and find the SLN. According to our data, a small incision can be made at the center of the area delineated by the hairline, the mid-axillary line, the edge of the pectoralis major muscle, and a line tangential to and 2 cm below the center of the hairline; 98.4% of SLNs will be found in locations 1 to 3. The concordance between the blue dye and radioisotope methods for the positive location of SLNs is 94.5%.10 We therefore suggest that our approach can be applied to the blue dye method.

The experience of the surgeon is an important factor in the accuracy of SLND.2; 11 ;  12 The identification rate is increased to 90–95% and the false negative rate decreased to 3.8–4.3% when the surgeon has performed more than 30 SLNDs.12 ;  13 The American Society of Breast Surgeons suggests that, before abandoning the procedure of carrying out axillary lymph node dissection after a negative SLND, SLND followed by axillary lymph node dissection should have been performed by the surgeon at least 20 times.14 Knowing the most frequent location of the SLN may shorten the learning curve for SLND and avoid unnecessary dissection during the operation.

According to a study by Cox CE,5 94% of SLNs are detected in a 5 cm diameter area centered on the crossing of the axillary hairline and the mid-axillary line (Fig. 4). In our study of 974 SLN biopsy procedures, in 98.4% of patients the hottest spot was located between the hairline, a line tangential to and 2 cm below the center of the hairline, the pectoralis major muscle, and the mid-axillary line. As shown in Fig. 4, this is a smaller area than that proposed by Cox CE5 and provides a more precise location of the SLN.


(A) Schematic diagram of the area in which 94% of SLNs are located according to ...


Figure 4.

(A) Schematic diagram of the area in which 94% of SLNs are located according to Cox CE5 (B) Comparison of this area (yellow) with the smaller area containing 98.4% of SLNs determined in our study (blue).

A study by Clough et al15 showed that 98.2% of SLNs are located alongside the lateral thoracic tributary of the axillary vein, either below (86.8%) or above (11.5%) the second intercostobrachial nerve, and no SLN is located in the area lateral to the lateral thoracic tributary of the axillary vein and above the intercostobrachial nerve, which is compatible with the location of hotspots seen before SLND in our study. This finding of Clough et al15 may help to avoid causing lymph edema by unnecessary dissection in this area. However, during an SLN biopsy procedure, the vessel and motor nerve cannot be visualized. Our finding may not only help the surgeon to find the blue node, particularly with a small incision, but also avoid unnecessary dissection in other areas.

A human cadaver study16 of the lymphatic anatomy of the breast showed that tracer injected into either the subareolar or intradermal location reaches the same first-tier node close to the lateral edge of the pectoralis minor muscle. This location is also compatible with our findings.

Preoperative assessment of the axilla by ultrasound is now widely accepted. If a preoperative ultrasound-guided biopsy procedure reveals a positive node, SLND may be avoided. Our finding should also be helpful in locating the lymph node in the axilla during ultrasound examination.

There is much discussion about an association between the site of injection (peritumoral, subdermal, intradermal, or periareolar) and the SLN identification rate.10; 17; 18; 19 ;  20 Suami et al16 suggested that subareolar or intradermal injection might miss other first-echelon nodes that can be identified by intraparenchymal injection. All the SLND procedures in our study were performed using intradermal periareolar injection and whether the results are influenced by the injection site deserves further study.

5. Conclusion

In the position of arm abduction from the chest wall of around 105°, flexion 15°, and elbow flexion, the most frequent location of the SLN identified by the radioisotope method is in the area demarcated by the hairline, a line tangential to and 2 cm below the center of the hairline, the pectoralis major muscle, and the mid-axillary line. We suggest that this area is carefully evaluated preoperatively by ultrasound for appropriate surgical planning. Once a positive node is noted preoperatively by ultrasound, then SLND may be avoided. Because SLND guided by the blue dye method is still performed worldwide, our findings should allow surgeons to make a small incision in this area and avoid the need for incision extension using blue dye method. If a blue lymph node is hard to identify intraoperatively, we suggest that the surgeon discloses the area closest to the pectoralis muscle. We believe this information will help shorten the learning curve required for a breast surgeon to perform SLND and allow easier identification of the SLN so that unnecessary dissection can be avoided.

References

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