CHAPTER 13
Integumentary System
251
CLINICAL CORRELATIONS
Figure 13-8A.
Malignant Melanoma.
H&E,
3
198.
Melanoma
is an aggressive malignant skin neoplasm
originating from melanocytes of the skin. It is charac-
terized by signiF
cant morphologic diversity, with skin
lesions of irregular shapes and various degrees of pig-
mentation. Melanoma metastasizes via the lymphatic
system. Malignant melanoma is less common than basal
cell or SCCs, but it causes the majority of deaths from
skin cancer. Genetic factors and sun exposure contribute
to the development of the disease. The most common
forms of melanoma include
superf
cial spreading mela-
noma
and
nodular malignant melanoma
. Melanoma
cells contain large nuclei with irregular contours, often
with prominent nucleoli. Treatment includes surgical
excision, chemotherapy, radiation therapy, and immu-
notherapy.
Figure 13-8B.
Melanocytic Nevus.
H&E,
3
22
Melanocytic nevi
, commonly referred to as “moles,”
may be congenital or acquired, and are composed of
melanocytes in
nests
at the dermo-epidermo junction, in
the dermis, or both. If the nevus cells are restricted to the
dermis, the lesion is referred to as a
dermal melanocytic
nevus
. If the nevus cells are present only at the dermo-
epidermo junction, the lesion is referred to as a
junctional
nevus
. If the nevus cells are present in both locations, the
term
compound nevus
is used. Moles typically appear as
raised tan to brown soft lesions on sun-exposed or sun-
restricted skin.
Dysplastic nevi
, which may transform
to malignant melanoma, are typically larger than most
nevi, may have irregular borders, and pigmentary varia-
tion. Microscopically, dysplastic nevi may show larger
junctional nests that fuse to adjacent nests and cytologic
atypia. This image shows a dermal melanocytic nevus
with no evidence of dysplasia or atypia.
Melanoma
(tumor) cells
A
Nests of
nevus cells
B
Type of Skin
Epidermis
Hair/Hair
Follicles
Glands
Sensory
Receptors
Location/
Distribution
Special Features
Thick skin
±ive layers;
thick stratum
corneum;
thick stratum
granulosum
No
Lack of
sebaceous
glands;
more eccrine
sweat glands
More receptors
Palms of the
hand and soles
of the feet
Thick epidermis:
thick stratum
corneum; stratum
lucidum present;
several cell layers of
stratum granulosum
Thin skin
±our layers; no
stratum lucidum;
single layer of
or no stratum
granulosum
Present in most
areas (except a
few places, such
as lips, labia
minora, and
glans penis)
Many
sebaceous
glands;
fewer
eccrine
sweat glands
±ewer receptors
Entire body
except thick
skin areas
Thin epidermis:
thin
stratum corneum;
stratum lucidum
absent; one layer
or no stratum
granulosum
TABLE 13-1
Comparison of Thick and Thin Skin
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