In skin biopsy, a biopsy site is selected, a skin specimen is removed, and the
sample is fixed and stained. It is necessary to select a site that is without
secondary ...
Go Back to the Top
Chapter
2
To Order, Visit the Purchasing Page for Details
Histopathology of the Skin
Skin biopsy is the most frequently used and important test for dermatological diagnosis. In a biopsy, a sample of skin is collected for observation under the microscope. There are many cases in which it is impossible to make a diagnosis based only on the clinical symptoms. A blister, for example, may be caused by various pathomechanisms, including viruses, bacteria and autoimmune diseases, or by heredity. It is often difficult to diagnose a blister just by naked-eye observation and disease history. To specify the cause of the disease and reach a final diagnosis, dermatopathological examination is essential.
A. Skin biopsy In skin biopsy, a biopsy site is selected, a skin specimen is removed, and the sample is fixed and stained. It is necessary to select a site that is without secondary changes and that is cosmetically acceptable. In inflammatory diseases, it is recommended to include the peripheral normal skin for comparison with the lesion. When a disease presents various lesions, it is preferable to collect multiple skin samples from different stages of inflammation. After local anesthesia, a biopsy specimen is removed (Figs. 2.1-1 and 2.1-2). The main methods for removing a sample are punch biopsy (clipping of a round sample), incisional biopsy (removal of a spindle-shaped sample with a surgical knife), and excisional biopsy (removal of the entire site). Shave biopsy (sample excision by razor blade) is another method for observing a lesion in the epidermis. The removed sample is fixed immediately with 10% formaldehyde to avoid secondary degeneration. The sample may be divided for cryo fixation or 2% glutaraldehyde fixation for an immunofluorescence test or electron microscopy. A skin specimen is prepared for hematoxylin-eosin (HE) staining. As shown in Table 2.1, various staining methods, known collectively as special staining procedures, are often used in combination. Immunostaining using monoclonal antibodies is also effective for diagnosis.
MEMO Skin biopsy may scar the site to varying degrees; therefore, the site and biopsy method should be chosen carefully, especially when it is performed on cosmetically important sites or on patients with a keloidal tendency. It is essential to record clinical conditions by photographing the biopsy site, as well as to obtain the patient’s informed consent by thoroughly explaining the necessity of the biopsy.
Preparation of a skin biopsy
27
Fig. 2.1-1 Procedure of skin biopsy. Punch biopsy.
2
28
2
Histopathology of the Skin
2
Table 2.1 Specific stains used in dermatology. Stain
Stained material
Hematoxylin and eosin Entire skin (HE) Elastica van Gieson
Fig. 2.1-2 Procedure of skin biopsy. Incisional biopsy with a surgical knife.
Stained color Blue (nucleus), magenta (cytoplasm, etc.)
Collagen fibers
Red
Elastic fibers
Black
Azan Mallory
Collagen fibers
Blue
Masson trichrome
Collagen fibers
Green
Periodic acid-Schiff (PAS)
Basement membrane Red
Toluidine blue
Glycogen
Red
Neutral mucopolysaccharides
Red
Fungi
Red
Mast cells
Purple (metachromasia)
Acid mucopolysaccharides Blue Alcian blue
Acid mucopolysaccharides
Blue
Sudan III
Fats
Orange-red
Congo red
Amyloids
Red
Dylon
Amyloids
Orange-red
Berlin blue
Hemosiderins
Blue
Kossa
Calcium
Black
Grocott
Fungi
Black-purple
Ziehl Neelsen
Mycobacteria
Red
B. Dermatopathology When observing a pathological specimen, it is necessary to identify the abnormality in the specimen by comparison with normal findings (Figs. 2.2-1 and 2.2-2). This section introduces fundamental terms for skin pathological changes and diseases.
a. Epidermis 1. Acanthosis (epidermal hyperplasia) a
b
c
d
e
f
g
Fig. 2.2-1 Normal skin (hematoxylin and eosin staining). a: Normal skin of the forearm. A basket-weaved horny cell layer is seen. Gaps between the stained horny cell layers are lipids that dissolved during fixation. These gaps indicate that the skin is well protected by moisturizing lipids.
h
i
j
k
l
m
n
o
p
q
Acanthosis describes thickening of the epidermis. It is classified into flat (the entire site thickens moderately; e.g., in chronic eczema), proriasiform (epidermal protrusions are extended), papillomatous (the epidermis projects upwards; e.g., with viral warts or seborrheic keratosis), and pseudocarcinomatous (pseudosquamous cell carcinomas project irregularly downward; e.g., chronic ulcer margin, deep mycoses) (Figs. 2.3 and 2.4).
2. Epidermal atrophy (epidermal hypoplasia) Epidermal atrophy (epidermal hypoplasia) is caused by reduction of keratinocytes (Fig. 2.5). It leads to thinning of the epidermis. As a result, the papillary processes are diminished or lost. It
Go Back to the Top
To Order, Visit the Purchasing Page for Details
r
