Seborrheic keratosis eyelid Seborreic keratosis appears to be "stuck onto" the surface of the skin. commonly it has a complex surface with numerous grooves. it may be pigmented and this should not be confused with melanoma. SK is common.; the sudden appearance of multiple, large seborrheic keratoses may be a dermatological marker of malignancy.

Seborrheic keratosis A. This roughened, brown, waxy lesion almost appears to be "stuck on" the skin. B. The lesions consist of an orderly proliferation of uniform, benign basaloid keratinocytes with a tendency to form keratin microcysts (horn cysts).

Actinic keratosis Most lesions form subtle zones of redness or sandpaper-like keratinization as seen in the lesions on the cheek, nose, and chin of this woman

Actinic keratosis with moderate dysplasia The lower portions of the epidermis show cytologic atypia, often with hyperplasia of basal cells with moderate dysplasia. There is hyper- and parakeratosis. Lymphocytes are present in superficial dermis

Actinic keratosis with Severe dysplasia

Solar (actinic) keratosis Sun exposure damages the skin, primarily as the result of ultraviolet light. This actinic damage is seen as a collection of abnormal collagen fibers in the upper dermis, seen here with a pale bluish appearance (basophilic degeneration) (arrows). Note the epidermal atrophy.

Squamous cell carcinoma A nodular and hyperkeratotic lesion occurring on the ear, unfortunately with early metastasis to a prominent postauricular lymph node (arrow).

Squamous cell ca skin Tumor of the face with rolled edges and depressed center.

SCC of the leg with exophytic appearance.

Well-differentiated SCC showing deep invasion The tumor is formed by atypical squamous cells arranged in orderly lobules showing large zones of keratinization.

Poorly- differentiated Squamous cell carcinoma showing spindle metaplastic features (sarcomatoid SCC)

Basal cell carcinoma This lesion is a prototypical pearly, smooth-surfaced papule with associated telangiectatic vessels The lesion is formed by multiple nodules of basaloid cells infiltrating a fibrotic stroma. The cells have scant cytoplasm, small hyperchromatic nuclei, and a peripheral palisade with clefting from the stroma. Note the similarity of these cells to the basal cells of normal epithelium.

Nodular and pigmented basal cell carcinoma of forehead Clinical appearance of pigmented basal cell carcinoma. Melanin is largely present in macrophages located in the stroma between tumor lobules.

Basal cell carcinoma lower lip a pearly pink border and an ulcerated center.

Basal cell carcinoma solid Nests of basaloid cells are dropping off into the upper dermis in this example of a basal cell carcinoma of the skin.