Keratinocytes in stratum spinosum, thin skin.
gets its name from the many small processes that seem to join neighboring cells with one another. The basis for
these spines is obvious in this transmission electron micrograph. Each cell is joined to its neighbors by numerous
), and the spines reﬂ ect the persistence of these connections after some cell shrinkage has occurred during processing of
the tissue. The electron dense tuft of material evident on either side of each desmosome is a bundle of
at the cytoplasmic faces of the desmosomes. The desmosomes and tonoF lament bundles are numerous and
more easily seen in the higher magniF cation view in the right-hand panel. As indicated by the extensive
in the nuclei of
these cells, the
are actively synthesizing proteins, most prominently subunits of
keratin f laments
, which will function
in establishing a tough, impermeable barrier layer at the surface of the skin.
Basal Cell Carcinoma.
Basal cell carcinoma
is the most common form of malig-
nant skin neoplasm. It originates from the basal layer
of epidermis and often occurs on sun-exposed areas.
Basal cell carcinoma rarely metastasizes and is usually
non–life-threatening if addressed early. Local invasion
may damage surrounding tissues causing cosmetic con-
cerns. Genetics and long-term exposure to ultraviolet
light and arsenical compounds contribute to the dis-
ease. Clinically, basal cell carcinoma appears as pearly
white nodules or waxy bumps on the face or neck with
telangiectatic blood vessels. Subtypes of basal cell car-
. Histologic features include a
of malignant basal cells with
and retraction of lobules from the surrounding
stroma. Treatment includes surgical
gery, curettage, and electrodessication.
Lobe of basal cell