The Skin - Pathology
Pathology of the skin is basically the same as those that occur in other organs. The changes that can be seen with the naked eye correlates well with that seen microscopically. The evolution of skin lesions can be readily followed by repeated biopsy.
The major functions of skin include sensory perception, protection against mechanical trauma, UV light and infection, insulation and temperature control, conservation of fluid, biosynthesis and excretion and aesthetic function. The morphology of the skin that appears simple at first sight is as complex and diverse as the 10 major functions of the skin - depending on the site, sex, age, race and environment.
Skin Biopsy: Select a site - not too early or too late but a fairly early representative lesion. Full thickness skin including the subcutaneous fat. The tissue is not to be grasped with forceps but a Gillies Hook (see below) to raise and maintain tension on the skin during removal.
Orientating the excised skin is important - it is helpful to press it gently - undersurface down on blotting papper before applying fixative (10% neutral buffered formal saline).
Reactive Changes in skin disease:
The skin has a limited range of responses to pathogenic agents and in many causes can result in similar responses. Inflammatory changes - eczematous reaction, erythema or granulomatous tissue response may be associated with many different aetiologies. Correlation of the histopathological features with the clinical history and naked eye appearances are extremely important to make a diagnosis.
Acantholysis: Loss of cohesion between epidermal cells (keratinocytes) with consequent formation of intra-epidermal spaces containing oedema fluid and detached, rounded epithelial cells.
Acanthosis: Thickening of the epidermis either focally or diffusely, due largely to increase of the stratum malpighii (Stratum Spinosum and Stratum Basali)
Dyskeratosis: Premature, abnormal or individual keratinisation of epidermal cells: the cells that loose their prickles and become rounded off, and the nucleus becomes pyknotic. This is seen in some rare benign conditions but more commonly in pre-malignant lesions and carcinoma of the epidermis.
The major functions of skin include sensory perception, protection against mechanical trauma, UV light and infection, insulation and temperature control, conservation of fluid, biosynthesis and excretion and aesthetic function. The morphology of the skin that appears simple at first sight is as complex and diverse as the 10 major functions of the skin - depending on the site, sex, age, race and environment.
Skin Biopsy: Select a site - not too early or too late but a fairly early representative lesion. Full thickness skin including the subcutaneous fat. The tissue is not to be grasped with forceps but a Gillies Hook (see below) to raise and maintain tension on the skin during removal.
Orientating the excised skin is important - it is helpful to press it gently - undersurface down on blotting papper before applying fixative (10% neutral buffered formal saline).
Reactive Changes in skin disease:
The skin has a limited range of responses to pathogenic agents and in many causes can result in similar responses. Inflammatory changes - eczematous reaction, erythema or granulomatous tissue response may be associated with many different aetiologies. Correlation of the histopathological features with the clinical history and naked eye appearances are extremely important to make a diagnosis.
Acantholysis: Loss of cohesion between epidermal cells (keratinocytes) with consequent formation of intra-epidermal spaces containing oedema fluid and detached, rounded epithelial cells.
Acanthosis: Thickening of the epidermis either focally or diffusely, due largely to increase of the stratum malpighii (Stratum Spinosum and Stratum Basali)
Dyskeratosis: Premature, abnormal or individual keratinisation of epidermal cells: the cells that loose their prickles and become rounded off, and the nucleus becomes pyknotic. This is seen in some rare benign conditions but more commonly in pre-malignant lesions and carcinoma of the epidermis.
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