Biomedical Engineering Reference
In-Depth Information
Case 7
Nevi
A 24-year-old man with type IV skin presented with a history of dark compound melanocytic nevi on the face. (Fig. 3.7A).
Initially he was interested in surgical treatment but did not want to have the lesions excised due to risk of scarring. Treatment
plan included monthly sessions with the diode (810 nm) laser. Lesions were treated at 1-month intervals as follows: session 1,
40 J/cm
2
and 20-ms pulse width; session 2, 40 J/cm
2
and 20-ms pulse width (double pulsed); session 3, 60 J/cm
2
and
30-ms pulse width (double pulsed). Cooling was left on due to the patient's type IV skin type. Dramatic clearing was noted
on follow-up at 11 weeks after the initial visit (Fig. 3.7B).
(
A
)
(
B
)
Figure 3.7
Nevi (
A
) before and (
B
) 11 weeks after treatment with the diode (810 nm) laser.
Congenital Melanocytic Nevi
Note: Laser treatment of CMN should be undertaken by those
with expertise in both melanocytic lesions and laser surgery.
CMN occur with a prevalence of 1.0-2.5% of newborns.
CMN are classifi ed by size: small, medium, and large. Small
CMN are those less than 1.5 cm; medium CMN are 1.5-19.9 cm
and large or garment CMN are those greater than 20 cm
in projected adult size. The risk of malignant progression to
melanoma is a particular concern for large/garment congenital
nevi, and classically has been estimated to be between 5 and
15%. However, data from a large meta-analysis suggest the risk
for malignant transformation to be signifi cantly lower at 2.5%
for large/garment sized congenital nevi (58). In addition,
nearly half of patients with a large/garment CMN have psycho-
logic or social diffi culties (59). Confl icting arguments have
been made whether laser treatment of CMN elevates or
decreases the risk of malignant transformation; however,
convincing evidence to either argument remains elusive. Thus
treatment of these CMN can be done more so for cosmetic and
psychosocial reasons.
QS lasers have been popular for treatment of congenital
nevi because of their nanosecond pulse durations that closely
match the thermal relaxation time of melanosomes. Reports
of QS ruby and alexandrite lasers demonstrate responses rang-
ing from poor to excellent. Multiple treatments are almost
always required and there is likely to be persisting nevus cells
in the deeper papillary dermis.
Long pulsed lasers have also been used to treat CMN due to
their potential to better target nests of melanocytes. Like QS
lasers, results have been variable to make defi nitive conclu-
sions. Combination treatment with both QS and long pulsed
lasers has also been reported with promising results (60). Abla-
tive lasers such as the CO
2
and Er:YAG lasers have also been
used alone or in combination with QS lasers.
Case 8
Congenital Nevus
This 7-year-old Asian girl presented with an unsightly nevus on her left upper lip. She was very self-conscious about its
appearance. It measured 6 mm in diameter and was without any clinical atypicality (Fig. 3.8A). After a discussion with her
mother regarding surgical excision and laser ablation, a decision was made to treat the lesion with a laser and watch it care-
fully for any atypical changes. The appearance after 4-monthly QS ruby laser treatments given at 4-5 J/cm
2
is shown in
Figure 3.8B. Six months later (Fig. 3.8C), the lesion began to recur. After three separate QS alexandrite laser treatments at
6-7 J/cm
2
given over 2 years, the lesion had almost totally resolved (Fig. 3.8D). Further treatments with the 5-ms long pulsed
alexandrite laser at 15-20 J/cm
2
were given to further improve the lesion and eliminate hairs within the lesion (Fig. 3.8E). The
