Sentinel Node Biopsy for Melanoma of Trunk; Wide Local Excision
Peter R. Jochimsen
Sentinel lymph node determination in patients with truncal melanoma presents its own peculiar problems because of the often ambiguous drainage of the truncal lymphatics. Although extremity melanomas generally go to the predictable regional nodes, the lymphatics of lesions of the trunk can unpredictably travel to unsuspected sites.
Sentinel node identification and removal is generally recommended for patients whose lesions measure 1 to 4 mm in thickness, in whom identification of nodal metastases might change management. Patients with lesions thinner than that generally do not have metastases. For patients with thick lesions, sentinel node biopsy or node dissection may be considered as appropriate.
Steps in Procedure
Sentinel Node Biopsy
View lymphoscintigrams and use gamma counter to identify site of nodes
In the operating room, inject 1 to 3 mL of isosulfan blue dye at site of primary tumor
Prep and drape nodal basin in usual fashion
Orient incision so that it can be excised should subsequent formal node dissection be needed
Identify node or nodes that are: palpable, or black, or radioactive, or that have taken up blue dye
Remove node(s) and obtain ex vivo count
Postexcision count in nodal basin should be less than 10% of ex vivo counts on node
Obtain meticulous hemostasis and lymph stasis, and close incision
Wide Excision
For in situ lesions, 0.5- to 1-cm margins are sufficient
For thicker lesions, 1- to 2-cm margins are required
Plan incision consistent with lines of skin tension, but also be mindful that reexcision may be required
Elevate disc of tissue containing lesion in subfascial plane
Close primarily
Hallmark Anatomic Complications
Error rate inherent in any sentinel node procedure
Lymphocele
List of Structures
Axillary lymph nodes
Inguinal lymph nodes
Umbilicus
Sentinel Node Biopsy (Fig. 97.1)
Technical Points
Because it takes 3 to 4 hours to optimize the distribution of the isotope, the patient is injected with about 0.5 mCi of technetium-99 sulfur colloid the morning of surgery, several hours before operation. This is done in the nuclear medicine suite, usually by the nuclear medicine physician.
If the primary lesion has had incisional or punch biopsy, injection should be done at four quadrants around the lesion. If the lesion has been completely excised, the midpoint of the incision is assumed to represent the region closest to the lesion, and the injection is done above and below that site. Intradermal injection is done essentially circumferentially around the site of the lesion (Fig. 97.1A).
Lymphoscintigraphy is obtained almost immediately and repeated at irregular intervals. Whole-body imaging is required for truncal lesions to ensure that ambiguous drainage or drainage to more than one nodal area is identified. An example is shown in Fig. 97.1B, which depicts drainage to an axillary
node from a lesion near the umbilicus. Occasionally, drainage to two nodal basins is identified (Fig. 97.1C) and must be investigated surgically. The nuclear medicine physician marks the skin overlying the identified nodes.
node from a lesion near the umbilicus. Occasionally, drainage to two nodal basins is identified (Fig. 97.1C) and must be investigated surgically. The nuclear medicine physician marks the skin overlying the identified nodes.
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