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Better staging: sentinel node mapping can help in head, neck melanoma.

SAN DIEGO -- Sentinel lymph node mapping of melanoma of the head or neck identifies the unusual lymphatic drainage patterns of these areas, improves staging, and helps identify candidates for adjuvant therapy, Dr. Jeffrey S. Eaton said at a melanoma update sponsored by the Scripps Clinic.

A review of data on 47 patients with head or neck melanoma treated at the clinic between 1996 and 2001 found that lymphoscintigrams performed 1-2 weeks before surgery identified lymphatic drainage patterns in 46 patients. The procedure failed in one patient because "some people just don't drain or the draining is very ambiguous," said Dr. Eaton of the clinic.

Although some surgeons prefer to get a lymphoscintigram on the day of surgery, he orders it a week or two in advance to discuss with patients how much surgery they'll be under-going--on one or both sides of the head or neck, or an axilla. "I think patients really appreciate that," even though sentinel node biopsies have not been proved to prolong survival, he said. A second injection of the radioactive technetium-99m used in lymphoscintigraphy on the morning of surgery acts as a tracer, but patients do not get scanned again.

Of the 46 patients with successful lymphoscintigrams, half showed lymphatic drainage from the melanoma lesion to the parotid basin. There were 15 patients with involvement of two or more lymphatic basins, including 10 with parotid and neck basin involved and 4 with drainage to separate basins on either side of the midline of the scalp.

With the preoperative lymphoscintigram plus intraoperative radioactive tracing and intradermal injection of a blue dye, surgeons identified sentinel lymph nodes in 44 patients.

Sentinel node biopsy requires a much more delicate technique in the head and neck than in other anatomic areas. These patients should be referred to someone with experience who does at least 15 sentinel node biopsies in the head and/or neck per year, he said.

The compressed anatomy of the head and neck makes it hard to differentiate a melanoma from an adjacent nodal basin. The lymphatics are more three-dimensional in the head and neck and more often have bilateral drainage. Surgeons must identify and preserve important neurovascular structures between superficial and deeper layers of lymphatics to do the procedure safely, Dr. Eaton said.

Intraoperative radioactive tracing and blue-dye injections are complementary, he noted. Salivary glands take up [.sup.99m]Tc, making the blue dye especially useful to visually identify involved nodes in the parotid basin.

Dr. Eaton injects [.sup.99m]Tc at a dose of 50-500 [micro]Ci, approximately 1/10 of mean doses used in the extremities. The low dose makes it easier to locate the sentinel node by decreasing background signals from the nearby primary lesion or other sites.

During the lymphoscintigram, it's helpful for the treating physician to be present in the radiology suite to make sure that both dynamic and static images are obtained of head and neck areas. Rotating the patient for different views will show how the radioactivity moves over time. The nuclear medicine team may not do this on their own, because "they're used to a static image, much like an x-ray," he said.

A 2-hour outpatient procedure, sentinel lymph node biopsy allows better histopathologic examination of nodes, compared with conventional surgical resection for melanoma.

After primary resection of the sentinel node, Dr. Eaton processes the skin margin by modified Mohs section with paraffin sections. He processes sentinel nodes individually because frozen sections waste valuable nodal tissue. He recommends more aggressive immunohisto-chemical analysis than average, including routine HMB-45 and S100 stains and serial step sectioning through the node. Usually only a portion of the node is involved.

BY SHERRY BOSCHERT

San Francisco Bureau
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Title Annotation:Clinical Rounds
Author:Boschert, Sherry
Publication:Internal Medicine News
Date:Mar 1, 2004
Words:614
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