The lymphatic system is a major conduit for the progression of many malignant and infectious diseases. Its Investigation has long been undertaken to diagnose the extent of disease and help plan treatment. Lymphoscintigraphy has many advantages over other imaging methods used to investigate the lymphatic system
The lymphatic system is a major conduit for the progression of
many malignant and infectious diseases. Its investigation has long
been undertaken in an attempt to effectively diagnose the extent of
disease and to help plan treatment. Imaging methods developed to
achieve this purpose include cutaneous lymphoscintigraphy, immuno-
lymphoscintigraphy, radiographic lymphography, and recently, MR
Of these procedures, lymphoscintigraphy currently provides many
advantages over the other imaging methods: minimal invasiveness,
short procedure time, low cost, and minimal patient preparation.
This article will address many important aspects of clinical
cutaneous lymphoscintigraphy, including agents, technique, and
The lymphatic vessels are distributed throughout most parts of
the body as a counterpart to the venous system. Its main components
are lymph capillaries, vessels, and ducts, extending from the
periphery to the central venous circulation. Lymphatic capillaries
are thinner than blood capillaries and lack basement membranes,
allowing increased permeability; they are blind-ending and are most
numerous below the epithelium of the skin and mucous
Lymph is transported centripetally to regain access to the
venous system through the thoracic and right lymphatic ducts. The
sites of lymphocyte aggregation and lymph filtration, the lymph
nodes are located along the lymph channels, predominantly in the
neck, axillae, mediastinum, periaortic, hypogastric, and inguinal
regions. The lymphatic drainage pathways in the extremities have
fairly defined routes, but variability persists.
Many investigators have demonstrated the lymphatic drainage in
the truncal region to be highly variable and unpredictable.2-4 Most
recently, lymphatic drainage investigation has further defined the
variable pathways, which appear predictable in the extremities and
individually unpredictable throughout the rest of the body;4 they
are displayed in figure 1. Lymphoscintigraphic evaluation allows
effective depiction of lymphatic drainage and increasingly has been
used in the evolving treatment options for some cancers, especially
malignant melanoma. Investigation has shown this nuclear medicine
procedure to be reproducible and effective.
Many radionuclides have been investigated and can be grouped
into three classes: radiolabeled macromolecules, radiocolloids, and
radiolabeled antibodies (table 1). Radiolabeled macromolecules and
colloids are the most commonly used agents; labeled antibodies are
investigational. Radiocolloid particle diameter of less than 50 nm
appears to be optimal for lymphoscintigraphy.5 These agents have
varied pharmacodynamics and imaging requirements. Although many
colloids have been investigated, only 99mTc sulfur colloid (SC),
99mTc antimony trisulfide colloid (ATC), 99mTc dextran (Tc Dx), 198
gold (Au-198) colloid, and radiolabeled antibodies will be
Au-198 colloid was the first agent to be documented to tract in
the lymphatics in 1953, although its investigation was focused upon
therapeutic treatment of lymphatic metastasis.6 Although the 2 nm
to 20 nm gold particle diameter was ideal,7 the long half-life of
2.7 days, 0.9 MeV beta particle, and energetic 412 keV gamma ray
were not desirable for dosimetry and imaging purposes.8,9 Also,
injection site radionecrosis has been documented.10
Dextran (99mTc Dx) has many desirable features for cutaneous
lymphoscintigraphy, such as particle size and controllable
biokinetics. Investigation has revealed glomerular filtration and
urinary excretion with dextran of weights less than 40 kilodaltons
(kd) after interstitial injection.11 Dextran is not phagositized,
enters the lymphatic system rapidly, and, due to the impermeable
characteristics of blood capillaries at molecular weights greater
than 40 kd, is a very suitable, specific lymphoscintigraphic agent.
Upon interdigital injection, knee/elbow and inguinal/axillary
activity were noted in approximately 12 and 98 seconds,
respectively, on dynamic imaging, and half-time activity at the
injection site was 31.5 minutes.12 These favorable features may
allow dynamic image acquisition when compared to other agents, but
it is not currently approved for use in the United States.
Sulfur colloid (99mTc SC) has been and continues to be used for
lymphoscintigraphy; this agent is the only approved agent for
cutaneous lymphoscintigraphy in the United States. Due to the large
colloidal particle size, ranging between 100 nm and 2000 nm,
variable lymphatic system visualization has been observed.
Injection site clearance of 30% is typical at three hours
postinjection, and dynamic imaging has been less satisfactory.9
Filtration of Tc SC has been performed to more optimally sized
particles, improving its lymphatic absorption.13 Also, recent
filtration attempts have been successful in producing reproducible
particle sizes ranging up to 50 nm (i.e., the size range identified
to be optimal for lymphoscintigraphy), and regional (inguinal)
lymph node identification in reasonable postinjection times (30
minutes) can be performed.14 The filtration procedure was simple
and performed with commercially available supplies, thus improving
scintigraphic features and potentially allowing for dynamic
Antimony trisulfide colloid (99mTc ATC) has also been
investigated. After being described in 1965,15 its physical size is
favorable and consistently uniform, ranging from 3 nm-15 nm to 40
nm.5,16 Like unfiltered Tc SC, moderate retention at the injection
site is present, approximating 40% at four hours
Also, Tc HSA has been employed. This agent demonstrates more
rapid migration from the injection site than observed with the
colloids. At 69 kd, its molecular weight is similar to that of
dextran. This allows almost immediate visualization of tracer
movement, allowing dynamic images and higher injection doses, which
improve image quality and potentially lower patient dose.9
When compared to Tc SC, Tc HSA has demonstrated improved image
quality, visualization of lymph channels, anatomic detail, and
decreased study time.17 As such, Tc HSA is the predominant
cutaneous lymphoscintigraphic agent employed at our institution,
although retention of activity in the sentinel node(s) may be
reduced compared to Tc SC.19 This could limit the usefulness of Tc
HSA with the use of intraoperative gamma probe, but it is proven
effective in static imaging.
Lastly, in an attempt to increase the sensitivity of detection
of tumor metastasis and improve tumor/background ratio,
immunolymphoscintigraphy has been studied with tumor-specific
monoclonal antibodies and kinetically with nonspecific antibodies.
It has been found that Ig classes (IgG and IgM), antibody fragments
[F(ab)2 and F(ab)], and colloids have similar lymphatic migration
rates (i.e., hours), which can be statistically increased with
motion (i.e., ambulation). Also, antibody migration rates differ
depending upon injection site, moving faster with limb injection
than body wall injection.18 Tc SC and Tc HSA are valuable
lymphoscintigraphic agents, providing high-quality images during
acceptable imaging times. Radiolabeled antibodies will require
further investigation to better define their future clinical
The equipment and materials required to perform cutaneous
lymphoscintigraphy are standard in any conventional nuclear
medicine department. The radiotracer used primarily at the
University of Alabama at Birmingham (UAB) is 99mTc HSA. The dose
ranges from 0.5 mCi to 1.5 mCi and should be diluted in 1.0 ml
sterile saline; larger doses in this range are utilized to
adequately encompass larger or more extensive lesions. Doses
ranging from 0.5 mCi to 2.0 mCi have been used with Tc SC and Tc
ATC. No specific patient preparation is required. Patients are
preferably preoperative, although postoperative studies are
commonly performed, especially due to our wide referral patient
population. Rubber gloves and reasonable semi-sterile technique
should be followed.
The injection site and surrounding area should be cleansed with
povidone-iodine or 70% alcohol. In the evaluation of melanoma, a
1.0-ml syringe and 26 ga., one-half-inch needle at 45° or less is
used to make several intradermal injections completely surrounding
the lesion, each producing a small wheal, ensuring intradermal
injection. If excisional biopsy has been performed, at least a
1.0-cm margin should be given about a lesion.
If lesions involve the head and neck, intradermal injections
should be performed at the superior aspect (distal from the trunk)
of the lesion. This has been proposed due to the inferior lymph
drainage of head and neck lesions and the fact that injections at
the inferior aspect of the lesion may potentially obscure sentinel
nodes due to close proximity of the sentinel node to the lesion.19
Also, attention to detail and accurate node identification is
particularly important because lymphoscintigraphy in the head and
neck has been noted to be more difficult than that performed in
other body regions.20
Intradermal injection is mandatory, as subcutaneous injection
may result in tracer entering into distinct, deeper lymphatic
channels, obviating the dermal plexus and not identifying the
sentinel node(s).21 Evaluations for lymphedema require pedal,
interdigital injection with immediate, one-hour, and three-hour
images. For breast cancer lymphatic definition, either deep
perilesional injection with ultrasound guidance and localization22
or paramidline, subxiphoid rectus sheath injections23 have been
The injection site needs thorough cleaning to remove any
potential contamination postinjection. The patient should
immediately assume a supine position under the gamma camera as HSA
migration usually begins rapidly (i.e., minutes). We continuously
image and supervise the examination to identify the initial lymph
node, although we archive only static images, usually requiring 30
to 60 minutes, for later intraoperative review. In our experience,
delayed images (i.e., several hours) are rarely needed; Tc SC
studies routinely require 2-to-4-hour delayed imaging.
One study revealed that all sentinel nodes were observed within
20 minutes postinjection using a colloidal agent.24 Images of the
regional nodal group(s) are obtained after sentinel node
identification. Also, if body wall lesions are being investigated,
images including the ipsilateral and contralateral
axillary/inguinal drainage basin should be performed to ensure
coverage, especially due to the variable body wall lymphatics
In our experience, imaging of the ipsilateral axillary or
inguinal nodal group for upper and lower extremity lesions,
respectively, has been sufficient (figure 3). Lesions of the head
and neck should include the upper thorax routinely (figure 4). If
migration is stagnant or slow, the injection site can be gently
massaged, promoting movement. Although evidence has been reported
with respect to truncal lesions, failed tracer movement from the
postoperative injection site has been documented (figure 5).25
Surgical division of the local lymphatics has been suggested as a
cause. The nature of the wide primary local surgical excision has
also been proposed. Although the cause has yet to be defined,
preoperative and postoperative lymphatic drainage basins can be
markedly different and completely altered and reconnection of these
transected lymphatic channels can occur by two years
Cumulatively, these data suggest that lymphatic drainage has a
dynamic feature, utilizing collateral pathways and a flexibility
similar to that frequently observed in the venous system.25 A body
wall outline is necessary for reference and can be performed with a
Tc point source. After identifying the sentinel node, orthogonal
images are obtained to help further define sentinel node depth;
point source localization on the skin surface is determined,
indelibly marked, and measured from a body landmark (i.e.,
umbilicus, iliac crest).
An alternative combined transmission-emission method has also
been described, which potentially may improve image quality and
eliminate errors in marker placement.26 This modification has also
been performed at our institution with very satisfying results and
minimal additional effort.
Most recently, postlymphoscintigraphic, intraoperative gamma
probe sentinel node localization has been investigated with very
favorable results.19,27 This has proved to be helpful, especially
in the head and neck region, to locate the correct nodal incision
site and to confirm that the radioactive node(s) has been
Also, the intraoperative gamma probe may help reduce unnecessary
nonsentinel node removal. As has been described, the intraoperative
gamma probe has been documented to be very helpful in localizing
foci of disease for surgical removal.29 This has been accomplished
as the probe assists the surgeon in locating intra- and
extraabdominal lesions, helps identify lesions too small for
scintigraphic detection and lesions not observed at surgery, and
provides evidence of the adequacy of surgical cancer resection.29
Cutaneous lymphoscintigraphy is a technically easy procedure, and
attention to detail allows reproducible sentinel node
identification for surgical excision with high accuracy.
Lymphoscintigraphy has many clinical applications. These
indications are listed in table 2. Recently, cutaneous
lymphoscintigraphy has received renewed emphasis as an adjunctive,
diagnostic modality in patients with malignant melanoma. The
surgical management of patients with malignant melanoma is varied.
Many investigators advocate elective lymph node dissection (ELND)
in patients presenting with stage I or II disease. Evidence has
been provided of decreased mortality from metastatic disease and
Conversely, others purport the benefit of local resection with
postoperative, short-interval evaluation, in patients with no
clinical evidence of regional lymph node metastasis.32,33
Relatively recently, a new paradigm of the progression of
metastases of malignant melanoma has been investigated, introducing
the sentinel node concept.21,34 This concept suggests that
micrometastases of malignant melanoma extend from the primary
lesion, gain access to the lymphatic system and progress to the
nearest node directly in the lymphatic channels, producing nodal
metastasis. Subsequently, malignant cells can migrate centrally as
the scope of the disease expands, initially from the sentinel node
to the regional group (echelon nodes), and then distantly.21
Other investigation35 supports this concept. Morton and Reintgen
discovered that the sentinel node was the site of metastasis in 18%
and the sole metastatic site in 87.5%; the presence of metastases
exclusive of the sentinel node was very remote, at 2 of 3079
nonsentinel nodes (less than 1%) and no skip metastases were
observed. No nodal metastases are presumed in patients with
disease-free sentinel nodes. If this surgical paradigm were
routinely adopted, with lymphoscintigraphic assistance, the
potential for decreased patient morbidity and cost, especially with
increasing cost-containment pressures, could be substantial,
possibly excluding prophylactic lymph node dissection in almost 80%
In addition, cutaneous lymphoscintigraphy affords additional
benefits. A more thorough and accurate depiction of lymphatic
drainage can be provided by this procedure over the historically
defined lymphatic drainage patterns. One investigator revealed 84%
discordance between lymphoscintigraphic drainage pathways and
established pathways, producing an alteration in patient management
Conversely, lymphoscintigraphy is imperfect. A recent study
specifically addressed this question.24 Repeat lymphoscintigraphy
demonstrated only 88% sentinel node reproducibility. In a small
series, Mudun has reported 50% discordance.37 Other researchers
report similar, marked discordances38 and identification of
different and new, additional sentinel nodes on sequential and
The nature of this variability is uncertain, although causes
have been suggested, including variable injection dose and volume,
tracer particle size, prior surgical intervention, site of lesion,
type (depth) of injection, timing of imaging, and image and display
parameters.19,39 Altogether, cutaneous lymphoscintigraphy can
provide an addition option in the surgical evaluation of
appropriately selected patients with malignant melanoma.
Breast and prostate carcinomas have been lymphoscintigraphically
investigated. Lymphoscintigraphy, via paramidline, subxiphoid
rectus sheath injections, has been evaluated and is a simple method
to define internal mammary nodal drainage.40,41 As elsewhere, the
parasternal lymphoscintigram revealed variability. This method has
been investigated in the radiation therapy planning of breast
In a recent study, an attempt to simulate the
lymphoscintigraphic methods applied to melanoma, via deep,
circumlesional breast injection, demonstrated 29 of 34 patients
with single, sentinel nodes ipsilateral to the breast lesion, no
contralateral breast sentinel nodes, and individually variable
breast lymphatic drainage.22 This investigation demonstrated that
lymphoscintigraphy can map breast lymphatic drainage in patients
with breast tumors, that this drainage is variable, and, as seen in
cutaneous lymphoscintigraphy, does not reliably follow classically
defined routes.22 This method requires further investigation and
could possibly influence the surgical approach to breast cancer if
favorable results develop.
Iliopelvic lymphoscintigraphy had been performed to evaluate its
efficacy regarding many pelvic malignancies, especially prostate
carcinoma. Two methods, pedal or perianal interstitial injections,
have been developed. The pedal method is technically easier,
although it fails to evaluate many nodal groups commonly involved
by metastatic prostate cancer (i.e., obturator, internal, and
Conversely, the perianal method identified these groups and has
shown disease-free predictive value of 90%.44 Due to the
questionable significance of nodal involvement45 and the possible
contribution of other metastatic routes (i.e., hematogenous)
unrelated to nodal disease,46 the current role of iliopelvic
lymphoscintigraphy is uncertain and further investigation is
Benign conditions have also been evaluated. Lymphoscintigraphy
has been used to evaluate cystic hygromas. The definition of
drainage in the pretreatment evaluation has been performed,47 and
the treatment options may include surgical excision, ablation with
sclerosing agent, or ligation. The proposed advantages of this
procedure allow determination of lymph source of the hygroma,
lymphatic morphology, extent of the hygroma, and rate of lymph
Furthermore, it has been used to evaluate and classify
lymphedema into primary forms (i.e., Milroy's disease, associated
with Turner's syndrome, neurofibromatosis) or secondary forms
(i.e., postoperative, post radiation treatment, or filarial
lymphatic involvement) and venous thrombosis.48,49 The reported
sensitivity and specificity of qualitative image interpretation
have been 92% and 100%, respectively, in diagnosing lymphedema.
With 99mTc ASC injection in the lower extremity, multiple varied
findings have been identified as abnormal.50
Although cutaneous lymphoscintigraphy is requested infrequently,
it is technically easy, minimally invasive, and potentially may
improve management, especially if performed with intraoperative
gamma probe techniques in patients with malignant melanoma. AR
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