by clear spaces. Entire cells gradually degenerate, and the epithelial connective tissue boundary is poorly defined.
Acantholysis. This lesion is caused by a separation of cells in the stratum spinosum so that an intraepithelial split occur, which leads to the formation of an intraepithelial vesicle.
Extension of Rete Pegs. Because of elongation, the rete pegs extend into underlying connective tissue.
Pseudoepitheliomatous Hyperplasia. In this condition, the rete pegs extend far downward, usually accompanied by acanthosis, to create a tissue pattern similar to carcinoma. However, the cells are essentially normal in size, shape, and chromaticity.
Dyskeratosis. This lesion shows an abnormal orientation or development of epithelial cells. Dyskeratosis or malignant dyskeratosis signifies a premalignant epithelial change, and the cells show such alterations as hyperchromatism, changes in polarity, and increased nuclear size with prominence of the nucleoli. Mitotic figures may also be increased. A benign type of dyskeratotic change or benign dyskeratosis occurs in conditions such as molluscum contagiosum and Darier's disease. Generally, however, the term dyskeratosis is used only for the malignant variety, to represent a premalignant lesion.
Necrosis. Necrosis refers to destruction of epithelium and replacement by an amorphous mass of tissue. Necrosis is usually produced by chemical action or by bacterial activity, as in fusospirochetal disease.
Ulceration. The ulceration is a break in the epithelial continuity due to destruction.
Connective Tissue Alterations
Infammatory Infiltration. In chronic inflammatory lesions the connective tissue is infiltrated by lymphocytes, plasma cells, histocytes, and scattered polymorphonuclear leukocytes. The inflammatory infiltrate may be homogeneously spread throughout the connective tissue, localized in a broad band close to the epithelium (as in lichen planus), or perivascular (as in discoid lupus erythematosus or syphilis). In acute inflammatory lesions, the primary cell of the infiltrate is the polymorphonuclear leukocyte. In ulcerated areas, the surface exudate contains large numbers of leukocytes. The presence of eosinophil leukocytes may suggest an allergic response or a parasitic infestation, but these cells are also commonly seen in healing macosal lesions. Multinucleated giant cells may be present in a foreign body reaction, and specific types such as Langhans' cells are highly suggestive of a tuberculous lesion.
Hyperplasia. Hyperplasia of connective tissue is characterized by an increased density of collagen fibers, as in diphenylhydantoin (Dilantin) reaction.
Collagen Degeneration. This is an important connective tissue change, characterized by a "coagulation" or clumping of collagen bundles so that the fibrous texture is absent. This condition is seen in radiation lesions and lupus erythematosus.
Vascularity. The number of capillaries and their engorgement with erythrocytes may be increased.
Mucous Gland Alterations. Obstruction of mucous glands by inflammation may result in acinar distention and ductal dilatation.
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