Squamous Cell Carcinoma.
Squamous cell carcinoma (SCC)
is the second most
common form of skin neoplasm. It originates from
keratinocytes of the epidermis. This carcinoma is
characterized by a slow-growing reddish or ulcerated
lesion with hard, raised borders. It is often found in
sun-exposed areas, with a high incidence in elderly
male Caucasians. Prolonged sun exposure, chronic
ammatory lesions, and genetic factors, especially
p53 tumor suppressor gene mutations, contribute to
the development of the disease. SCCs called
commonly arise in premalignant lesions on
sun-damaged skin. Carcinoma cells have enlarged and
hyperchromatic nuclei with variable differentiation,
some lesions producing abundant keratin. Treatment
includes surgical excision, cryosurgery, electrosurgery,
radiation therapy, and topical treatment.
Stratum corneum of the epidermis, thin skin.
is the F nal product of the proliferation and differentiation that take place in the deeper layers of the epidermis. The
dead cells (
) of the stratum corneum have lost the usual organelles and have become F lled with mature
, a tough net-
work of keratin intermediate F laments that are cross-linked by the protein F laggrin. Keratin and the persisting
account for the mechanical strength of the epidermis. Contributing to the relative impermeability of the stratum corneum is a coating of
involucrin linked to the inner surfaces of the plasma membrane and the presence of lipid that has been secreted into the spaces between
cells. In this specimen of thin skin, the
is only one cell thick, and some of its characteristic features (
) are not clearly discernible. Bundles of
can be distinguished.
Nucleus of stratum