The presence or absence of
lymph node metastases is the
most significant prognostic factor
for survival and recurrence in malignant
melanoma. Lymph node disease
decreases the 5-year survival by 40%
to 50%. The number of metastatic nodes
and whether nodal metastases are clinically
occult or apparent are independent
predictors of survival.
Sentinel lymph node (SLN) mapping
was developed in the early 1990s as a
relatively noninvasive method of staging
the draining lymph node basins
from primary melanoma. The process
helps to select patients who may
benefit from a lymph node dissection
and systemic therapy. The majority
of SLN mapping studies in melanoma
have included few children[2,3]
and few patients with thick lesions
(≥ 4 mm).[4-6] The Bisseck/Shen/
Pranikoff article raises the following
questions regarding SLN mapping:
What are the success rates and safety
of lymphatic mapping in the head and
neck region? Is SLN mapping justified
in the management of primary
melanomas with a tumor thickness
≥ 4 mm?
Melanoma in Children
Melanoma in children accounts for
0.3% to 4% of all new cases of melanoma
in the United States each year.
It rarely occurs before puberty and is
responsible for 1% to 3% of pediatric
malignancies. Risk factors include the
presence of giant congenital nevi,
transplacental spread of maternal melanoma,
and xeroderma pigmentosa.
There is no clear evidence that melanoma
is more aggressive in children.
Spitz nevi are more common in children
than in adults and preferentially
involve the head and neck. They may
be hard to distinguish from melanoma
with Spitz-like features. The biologic
behavior of atypical spitzoid melanocytic
lesions has not been elucidated.
Su et al reported their experience with
SLN biopsy in 18 patients with problematic
spitzoid melanocytic lesions.[
8] Of these patients, 11 were less
than 18 years of age; 6 of the 11 (54.5%)
had SLN metastases and underwent a
SLN Mapping in Thick Melanomas
The use of SLN mapping and biopsy
in the management of thick melanomas
(≥4 mm) has been questioned
because of the perceived poor prognosis.
These lesions are believed to
be associated with a high incidence of
occult regional and distant metastases.[
9] No prospective randomized trials
have demonstrated a survival
benefit for patients with thick melanomas
who underwent routine elective
lymph node dissection.
A recent review by Kim et al of
120 patients with thick melanomas
found that nodal status was an independent
predictor of survival.
Nodal status was found to be the
strongest predictor of survival in three
recent reviews involving patients with
melanomas ≥ 4 mm thick treated by
SLN biopsy.[4-6] In the Emory experience
of 114 patients with thick melanomas,
the 3-year overall survival
for SLN-negative patients was 82%
and for SLN-positive patients, 57%
(P = .006, Figure 1).
Head and Neck Melanoma
Most series of lymphatic mapping
studies have concentrated on melanomas
of the trunk and extremities rather
than of the head and neck. The head
and neck has a rich and unpredictable
lymphatic system, and excisional biopsy
in this area can be technically challenging.
The region contains over
one-third of the body's lymph nodes.
O'Brien et al found a 34% discordance
between the clinical prediction of lymphatic
drainage and the lymphoscintographic
findings in 97 cases of head
and neck melanoma. In 33% of
cases, there was drainage to the lymph
nodes within the parotid gland.
Several problems are associated with
SLN mapping in the head and neck
region. Background radiation from the
primary injection site can incorporate
the SLN, making localization at preoperative
Lesions on the cheek can obscure parotid
drainage, and lesions of the neck
can shadow drainage to the internal
jugular nodes. Lower doses of radioactivity
are used in the head and neck
region to compensate for these events.
The technetium-99m sulfur colloid used
for mapping is absorbed by the salivary
glands, thus increasing the background
radiation in the parotid nodal bed. Sentinel
lymph nodes in the parotid gland
tend to be small, which makes intraoperative
localization more difficult without
the use of blue dye. There is also
concern that the facial nerve can be
injured during the process.
Ollila et al reviewed their experience
with parotid SLN mapping in 39
patients. The SLNs were successfully
identified in 37 patients (94.9%),
and one case of temporary facial nerve
paresis was reported. Despite these limitations,
many authors have reported a
high rate of success with SLN mapping
in the head and neck region.[13-19]
A very small percentage of melanoma
cases in the United States occur
in children. The indications for SLN
mapping in children should be the
same as for adult patients. The head
and neck region is associated with
several limitations to successful SLN
mapping, which can be overcome with
a knowledgeable nuclear medicine
department and surgical experience.
The SLN status of patients with thick
melanomas (≥ 4 mm) is the strongest
predictor of survival and should be
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