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Hyperkeratosis is manifested clinically as skin thickening, and sometimes whiteness. It is due to a hypertrophy of the stratum corneum, the outer skin layer. Histologically, there is an increase in thickness of the keratin layer, devoid of nuclei. Here hyperkeratosis is seen in lichen sclerosus. |
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| 2. |
Parakeratosis - incomplete keratinization of the stratum corneum, with presence of pyknotic nuclei. Parakeratosis in a case of melanosis. |
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| 3. |
Acanthosis - increase in the keratinocytes of the spinous layer with thickening of the epidermis. Seen clinically as papules and plaques. Histologically there is thickening and fusing of the rete pegs. Also seen here is spongiosis. |
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Spongiosis - Nonspecific, and may be seen with eczema, allergic contact dermatitis, and other conditions. There is widening of the interspace among keratinocytes due to intercellular edema without detachment of the cells from each other. If spongiosis is severe, it can cause intraepidermal vesicles. |
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Acantholysis - There is loss of cohesion among prickle layer cells. The cells become round, due to dissociation of the intercellular bridges. May be seen in several conditions including pemphigus vulgaris and viral infections. |
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| 6. |
Lichenoid - a band-like chronic inflammatory infiltrate in the papillary dermis, as seen in lichen planus. |
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| 7. |
Papillomatosis - wavy projections of the epidermis and dermal papillae. Clinically it manifests as the presence of multiple warty or bumpy structures, as seen in condyloma acuminatum. |
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| 8. |
Dyskeratosis - cell death with premature and abnormal keratinization of individual epithelial cells, below the layer of the stratum granulosum. Histologically, the cells appear of orange or dark pink color, small size and abnormal shape. Seen in condyloma acuminatum and squamous cell carcinoma. Here dyskeratosis is seen in a case of differentiated VIN. |
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| 9. |
Pleomorphism - cell population showing individual morphologic variation, with different size and shape of nuclei. It is seen in association with malignancies. |
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| 10. |
Koilocytosis - intermediate or superficial cells showing nuclear atypia, often with a wrinkled “raisin” appearance, surrounded by a large, clear and irregular perinuclear halo with clear-cut borders, and thickened peripheral rim of cytoplasm. The nucleus is enlarged (2-3 times the size of a normal intermediate cell). Binucleation is common. Pseudokoilocytosis can be found in different situations (infection, post-menopause, pregnancy, etc) Koilocytosis is the cytopathic effect of HPV and is pathognomonic for HPV infection. |
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