Sentinel Node Localization by Lymphoscintigraphy: A Reliable Technique with Widespread Applications

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Abstract
The concept of the sentinel lymph node (SN) represents an important contribution to guide appropriate surgery of cancer. Diagnostic non-invasive or minimally invasive procedures that provide accurate preoperative staging of the lymph node status are badly needed. The technique of SN biopsy, first developed with the purpose to select melanoma patients for regional node dissection, has been extended to other malignancies. Initial studies in breast carcinoma, conducted with vital blue dye, showed that the SN concept was biologically valid, although SN was missed in up to 30%–40% of cases. If a radioactive tracer is injected close to the tumor, then the SN can be identified by lymphoscintigraphy (LS), and a gamma ray detecting probe (GDP) can be used to locate the skin projection of SN and assist biopsy. These techniques are already used successfully in melanoma and breast carcinoma where the various parameters involved, such as the size of the radioactive particles, the injection site and injection volume, have recently been optimized. In a large series of breast cancer patients, the overall predictive value of the SNs biopsy guided by LS and GDP was 96.8%; in patients with small carcinomas (<1.2 cm diameter), the concordance between SN and axillary status was 98.6%. In patients with melanoma, LS combined with GDP showed itself to be superior to the blue dye mapping. LS associated with GDP allowed the detection of SN in 98% of cases and 72 SNs in 54 basins were localized. Using blue dye instead, SN was stained only in 80% of patients (50 SNs in 40 basins). Lymphoscintigraphic techniques have shown promising results also in tumors such as vulva and tongue. In conclusion, LS is a simple nuclear medicine technique, relatively inexpensive and well accepted by patients. SN biopsy guided by a GDP is becoming widely adopted for a variety of neoplasms, contributing significantly to the search for less aggressive treatments in patients with early stages of cancer.