Lymphatic mapping: finding the sentinel node
Lymphatic mapping can identify the sentinel node in 90% to 95% of patients with solid tumors, making it possible to detect smaller metastases than ever before. Among the latest techniques are preoperative lymphoscintigraphy and intraoperative mapping and node removal.
Lymphatic mapping is not recommended for patients with advanced tumors and no obvious injection site, patients with grossly involved lymph nodes, or patients who have undergone previous vulvar or groin surgery that may have altered the lymphatic drainage. Because wide local excision may interfere with lymphatic mapping in patients with vulvar cancer, it is advisable to perform only a punch biopsy when suspicious vulvar lesions are present before referring the patient to a gynecologic oncologist.
TABLE 1
Lymphatic mapping of the vulva: results of published series
| SERIES | PATIENTS IN WHOM SN IDENTIFIED(%) | TOTAL NUMBER OF CASES | GROINS IN WHICH SN IDENTIFIED(%) | TOTAL NUMBER OF GROINS |
|---|---|---|---|---|
| Barton et al15 | 90 | 10 | — | Not stated |
| DeCesare et al16 | 100 | 11 | 100 | 14 |
| Terada et al17 | 100 | 9 | 100 | 12 |
| DeCicco et al13 | 100 | 37 | 100 | 55 |
| Ansink et al18 | Not stated | 51 | 56 | 93 |
| de Hullu et al12 | 100 | 59 | 89 | 107 |
| Levenback et al14 | 88 | 52 | 75 | 76 |
| SN=sentinel node | ||||
Cervical cancer
The cervix is a midline structure with complex lymphatic drainage. Thus, in patients with cervical cancer, an extensive nodal dissection is required to remove all potential sites of metastatic disease. Regional therapy is curative if the extent of disease is accurately established.
Several feasibility trials have been reported.19-25 In addition, the first laparoscopic gamma probes are now available, allowing 2 minimally invasive techniques to be combined: lymphatic mapping and operative laparoscopy.
Unfortunately, questions remain about the usefulness of lymphatic mapping in cervical cancer patients. That is because lower-extremity lymphedema is not as common following pelvic lymphadenectomy as it is following inguinal femoral lymphadenectomy. However, the determination of lymph node status could help triage patients between radical surgery and regional radiotherapy.
Future directions
In the coming years, gynecologists should look for increasing use of lymphatic mapping in patients with solid tumors. One of the great promises of lymphatic mapping is the ability to detect smaller and smaller metastases. For example, investigators have found human Papillomavirus DNA and cytokeratin RNA in lymph nodes from cervical cancer patients with “negative” biopsy findings after standard histologic examination. The clinical significance of these socalled biologically positive lymph nodes is not known at present. However, there will be increasing application of new molecular biologic techniques to the analysis of sentinel nodes.
The author reports no financial relationship with any companies whose products are mentioned in this article.
