Eyelid pathology appears commonly in the examination. This
section lists some common terms used to describe microscopic changes in
the skin. Many other terms are not included here as their changes are seldom
seen in the eyelid.
Acanthosis
Thickening of the epidermal layer. This usually refers to an increase
in the number of prickle cells (keratinocytes which lie above the basal
layer). This occurs in seborrheic
keratosis.
Hyperkeratosis
This refers to an increase in the amount of keratin. Clinically, this
appears as scale or horn on the surface of the lesion. This can occur in
many different lesions both benign or malignant. In order to obtain an
accurate diagnosis, it is important to remove the underlying structure
ie. the epidermis for histology.
It is seen in:
Parakeratosis
This term refers to the retention of nuclei within the keratin layer.
This sign indicates shortened turn-over of the epidermis. This occurs in
actinic
keratosis.
Dyskeratosis
This term refers to cell keratinization within the epidermis rather
than at the surface as is normally the case. An aggregate of such cells
form the keratin pearl or eddy. It is seen in squamous
cell carcinoma.
Dysplasia
It is used to describe cells that show aberrant growth and differentiation.
It is reflected microscopically by nuclear hyperchromasia and increased
cell size (disordered differentiation) and increased number (aberrant growth).
Dysplastic cells lie in a continuum between benign and fully malignant.
In the epidermis, dysplasia arises in the basal keratinocytes and is
reflected by disorganization and enlargement of the cells. Clinically and
microscopically this lesion is called an actinic
keratosis. If the process of malignant transformation continues, the
dysplastic cells become fully malignant, invade the dermis, and are now
capable of spread beyond the skin (metastasis). Once the malignant cells
have invaded the dermis, the lesion is termed squamous
cell carcinoma (reflecting the cell of origin).
