Biomedical Engineering Reference
In-Depth Information
Blue Nevus
Blue nevi are usually solitary, discrete, well-circumscribed pap-
ules 1-8 mm in diameter that arise spontaneously, most often
in children and young adults. The male-female ratio is approx-
imately 2:1. The melanin-producing cells are deep within the
dermis and their blue-black color results from the Tyndall
light-scattering effect of the overlying tissues.
Histologic examination shows an extensive number of
spindle-shaped, elongated melanocytes within the middle and
lower dermis, occasionally extending into the fat. These cells
may be grouped in fascicles between collagen bundles and
tend to aggregate around adnexal structures, nerves, and blood
vessels.
Because of their benign nature, blue nevi are usually
removed for cosmetic reasons. Although extremely rare,
malignant blue nevi have been reported. The primary method
of removal of these lesions is local excision. Similar to treat-
ment of nevi of Ota and Ito, the QS ruby, alexandrite, and
Nd:YAG lasers should also be effective in removing these deep
dermal melanocytes, as long as the lesion does not extend into
the subcutaneous fat (64-69). Biopsy should be strongly con-
sidered for lesions which are new, multinodular, or plaque-
like, or changing. Rare cases of malignant melanoma arising
from cellular blue nevi have been reported. Cellular blue nevi
should therefore be excised because of this rare but potential
risk for malignant transformation.
The only mode of treatment mentioned in the literature is
with the QS ruby laser (69), although all three QS lasers are
effi cacious, similar to their use with the nevus of Ota and Ito.
Again, the longer-pulsed ruby and alexandrite lasers may
prove effective.
694, 755, and 1064 nm for better depth of penetration. Larger
spot sizes also enhance the penetration depth. Unfortunately,
pigmented lesions respond variably to lasers, and for any indi-
vidual patient it is diffi cult to predict the treatment outcome.
Epidermal lesions treated with the QS lasers should have
immediately visible superfi cial whitening, often associated
with a slightly eroded surface, which heals over the course of
approximately 7-10 days. The patient should be advised that
the treated area may appear darker in color as it heals. If the
lesion is treated with the QS Nd:YAG laser (532 nm), purpura
may develop from the rupture of blood vessels due to the coin-
cident absorption of hemoglobin and melanin at this wave-
length. If an urticarial response to treatment is noted, the
patient may require oral antihistamines and premedication
with oral antihistamines should be considered prior to the
next treatment session. The patient should be advised to wash
the area daily with mild soap and water and cover with a layer
of petrolatum or antibiotic ointment.
clinical pearls
Atypical lesions should be carefully examined by a dermatologist
and biopsied. When approaching pigmented lesions, a high level
of suspicion should be maintained so that worrisome lesions are
not overlooked, and appropriate treatment not delayed.
management of complications
The risks of laser surgery include transient hyperpigmentation
or hypopigmentation, scarring, permanent hyperpigmenta-
tion, incomplete clearance of treated lesion, and recurrence.
Treatment of pigmented lesions is often done for cosmetic rea-
sons. In selecting a therapeutic regimen, optimal esthetic result
must be the goal in choosing the most appropriate treatment
with minimal risk. Ideally, it must be both effective and free
from the adverse sequelae of scarring and permanent pigmen-
tary complications. This can be best achieved by selective tar-
geting of pigment-containing cells. Should blistering of the
treated area occur, local wound care should be administered. In
an effort to minimize the risk of hyperpigmentation following
laser treatment, the patient should be counseled on sun protec-
tion measures, including the use of broad spectrum physical
sunblocks such as those containing micronized zinc dioxide.
If hyperpigmentation is noted within the healing irradiated
sites, hydroquinone therapy should be used two times per day
until it resolves. Avoidance of sun exposure and use of a UVA/
UVB sunblock to minimize postinfl ammatory hyperpigmen-
tation are recommended. If hypopigmentation does occur, it
often resolves spontaneously with time. If not, the excimer
laser or other narrow band UV source may be utilized. In the
rare event of adverse sequelae such as scarring, it is best to
implement early treatment with the pulsed dye laser.
Patient Selection
When determining whether a patient with a pigmented lesion
is appropriate for laser treatment, the patient's dermatologic
history must be evaluated. Consideration must be given to the
patient's Fitzpatrick skin type and its innate tendency to
hyperpigment in response to infl ammation.
Patients should be educated regarding the laser procedure so
that they have realistic expectations. Patients should be advised
of potential side effects, including hyperpigmentation, hypopig-
mentation, temporary or permanent textural change, scarring,
or recurrence. Showing patients photographs of similar lesions,
immediately post treatment, after a few treatment sessions, and
fi nal clinical result, will increase their awareness of what to
expect. It is also helpful to show examples of patients with aver-
age results, not complete clearing, so that patients are aware of
the range of possible outcomes. It should be clearly stated that
not all lesions can be removed completely and that successful
lightening may require several treatment sessions at 6-week
intervals. In addition, the unknown risk of melanoma forma-
tion must be addressed for all melanocytic lesions.
future directions
The optimization of laser parameters, refi nements in tech-
nique, and a better understanding of the underlying biology
may further help clinicians to treat these lesions more effec-
tively. The role of fractionated photothermolysis in improving
certain types of pigmented lesions is forthcoming, and the
potential use of picosecond lasers also holds promise for the
treatment of pigmented lesions.
Laser Selection
Laser Technique
Most benign pigmented lesions respond fairly well to laser
treatments. Those located more superfi cially can be treated with
the shorter wavelengths of 510 and 532 nm, as well as 694 and
even 755 nm. Deeper lesions require the longer wavelengths of
