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TAKE-HOME NOTE: when you surgically dissect to find the SLN, remove all nodes that are easily available...especially when palpably suspicious as a way to reduce the SLN false negative rate; it adds little or no morbidity⁶.

The status of the axillary lymph nodes is one of the most important assessments in breast cancer. But, complete or extensive axillary lymph node dissection (ALND) is not without consequences. Especially because of the complication of lymphedema of the arm of the dissected axilla, the intensity of dissection (such as skeletalization of major veins and artery) began to be reduced unless there was reason to believe that widespread node positivity was likely. Since a very significant percentage of axillary dissections had been negative (by old-style pathology processing), it was proposed that the first node draining the cancer could be tested and stand as an accurate surrogate for axillary node status. This node is the "sentinel lymph node" (SLN). So, efforts have been made to use the lymph node nearest the tumor (the lowest node)  or the initial node reached by breast lymph fluid (the sentinel lymph node...SLN) and use the status of that node as a surrogate for the status of the axillary nodes. 

• Why remove axillary lymph nodes?

  1. Diagnostic/staging reasons:

     • stage for prognosis (extremely powerful predictor)

     • determination of number of positive nodes, % of total nodes positive, volume of metastatic disease, and whether mets are all intranodal or amount of extranodal positivity bear on various decisions about medical and radiation treatment protocols

  2. Therapeutic reasons:

     • to debulk gross disease (adjuvant treatment less good against macroscopic residual disease)

     • ALND reduces local recurrence

     • positive ALND triggers cytotoxic chemo.

     • positive ALND may trigger extension of XRT to axilla & supraclavicular areas

• Complications of ALND:

  1. lymphedema (6-20% of cases)

     • troublesome condition of arm swelling and special measures which must be taken to control it once it is a problem

     • rare cause of lymphangiosarcoma

  2. neuropathy: skin numbness and/or dysesthesias in 47%, usually gone in 12 months

  3. intercostobrachial syndrome (severe protracted pain), rare

  4. immediate post-operative morbidity problems not uncommon

  5. adds a medical cost impact of around $10,000 per case (CY1999)

• "Pros" of SLN biopsy usage:

  1. avoid above ALND complications and adverse consequences

  2. SLN is a low, closest node and first node to have a metastasis in a VERY high percentage of cases

  3. situations favorable for SLN biopsy:

     • large (by imaging) d-CIS cases

     • cases with d-CIS histology on core biopsy, but, by imaging, suspicious for microinvasion or invasion (a type of discordance)

     • T1 lesions only have from 0-3% ALN positivity

• "Cons" of SLN biopsy usage:

  1. SLN not always an accurate surrogate because:

     • metastases may skip the SLN (a false neg. SLN [LMC-01-242; 924; 7037])

     • node sinus IHC positive epithelial cells may not signify a "positive node" (real met. vs. "mechanical dislodgement")

• Surgical skill development: it takes somewhere between 20-36 cases done "on protocol" (SLN biopsy followed by ALND) to get the procedure down for accurately removing the actual SLN. The first cases at LMC were LMC-98-3400^melanoma, 3473^breast, & 4242^melanoma.
  
• Finding the SLN:
  
  • Goal: surgical performance of SLN skilled enough to find the SLN in at least 90 out of 100 cases
    
  • Marker agents (some surgeons use both simultaneously):
    • Dye: may be messy but no special equipment needed
    • Radioactive: should follow OSHA & DHEC rules; but technetium 99 essentially harmless as beta rays (see AJSP 24(11):1549-1551, 2000)
      
  • Technique: peritumoral vs. peri-areolar intradermal, with or without breast massage
    
  • Failure to localize can be due to the fact that the SLN is filled with tumor, "stopped up", nonfunctional as to lymph flow [LMC-01-5654]
    
  • Location of the SLN:
    
    • axilla: 97% (1434 0f 1470 cases@ Moffitt) [about 90% are in the triangle between lateral border of pectoralis major, the medial border of the lattissimus dorsi, and the inferior margin of the hair-bearing axillary skin]
      
    • internal mammary chain: 3% (36 0f 1470 cases@ Moffitt) [medial and retromammary areas more likely go this way]

• Frozen section (or rapid touch prep) status report:

  • Why? If positive, axillary dissection is indicated and may be done in the same surgical and anesthetic episode for further diagnostic/staging info and/or therapeutic (debulk the axilla) reasons.

  • When? Only when the surgeon removes the SLN and, on visual exam, is highly suspicious of metastatic disease in the SLN (but, we readily defer to surgeon's choice).

  • Accuracy? FS positive has a high degree of accuracy; but negative is never negative...it is indeterminate. True negative for our lab is when the permanent section intense protocol finds the node to be negative.

• Permanent section processing: serial section at 2 mm. and stepcut the block

• Positive status: be careful to apply correct histological criteria

• False positive & false negative rates, conventions:

  • Correct calculation: the rate is properly calculated as false+/total+ or false-/total-. False negs, see above.

  • Target (a full-court-press method): false negative rate of 6% or less (Cancer 85:2433-38, 1999; Milan, Italy, 155 T1-T2 cases with clinically negative axillae; SLN total frozen section with entire step cuts and H&E plus IHC at each level, average 65 minute effort; 70 pos. cases, 17 as micromets 2mm. or less in size & 85 neg. cases, 5 of which had a pos. level 1 node)

• Positive SLN findings indicating likelihood of other positive ALNs:

  1. Macroscopic positivity

  2. Transcapsular invasion

References:

1. Alden Sweatman, a speaker, 6th Annual breast Symposium, Columbia, SC
   18 May 2001
2. Krag, 1998 multicenter SLN paper
3. Kelly McMaster (Louisville), Ann. Surg., page 676-684, 2001.
4. 23rd annual San Antonio Breast Cancer Symposium, Dec. 6-9, 2000, in Breast Cancer Research & treatment 64(1):1-151 [from group at Chapel Hill).
5. Yared MA, et. al., "Recommendations for Sentinel Lymph Node Staging in Breast Cancer", Am. J. Surg. Path. 26(3):377-382, 2002.
6. Chapgar AB, et. al., Arch. Surg. 142:456-460, May 2007.