Information on the skin biopsy
Selecting the biopsy technique
Biopsy of inflammatory dermatoses
In the case of inflammations, it is often
possible to make a diagnosis on the strength of superficial
changes (para-keratosis mounds stacked one on top of another,
with deposition of neutrophile granulocytes in the case of
psoriasis, cornoid lamella in the case of poro-keratosis,
loss of the horny layer with superficial acantholysis in the
case of Pemphigus foliaceus). In over two-thirds of all inflammatory
dermatoses, pathological changes are confined to the epidermis
and upper half of the dermis, and are thus amenable to being
recorded complete by a shave biopsy. The problem is that in
cases of inflammatory dermatoses, differential histopathological
diagnosis is even more difficult and all-inclusive than is
the case with malign neoplasias, and the histopathologist
must therefore see the
 entire
dermis in most cases in order to make a judgement
with confidence.(4)
A representative cross-section through the
entire dermis is best obtained by a punch biopsy, which, unlike
a shave biopsy, extends sufficiently deep and, unlike the
spindle biopsy using the same biopsy volume, includes a broader
cut into the dermis. As a rule, a 4mm punch will suffice.(1)
Smaller punches certainly allow a diagnosis in many cases,(20)
though confidence in the diagnosis is significantly lower.
In particular, focal changes can be conclusive in difficult
differential diagnoses, which are frequently not apparent
in small biopsates, for example foci of para-keratosis and
some eosinophile granulocytes for the demarcation of lichenoid
medication exanthema of Lichen planus or small agglomerations
of lymphocytes inside the epidermis for
early diagnosos of parapsoriasis in plaque. In
the case of bullous dermatoses, the punch should be significantly
larger than the blister to be removed, as otherwise the force
of the cut caused by rotating the punch can lead to accidental
removal of the blister cover. Should the blisters present
not be sufficiently small, a 6mm punch or spindle biopsy should
be chosen.(1) In cases of alopæcia, also, the biopsy
on the hirsute head should be performed with a 6mm punch,
in order that sufficient follicles can be assessed. The biopsate
should contain as much fatty tissue as possible, particularly
for alopæcias in which the bulbi of the terminal hair-follicle
must be assessed, and where there is a clinical suspicion
of diseases associated with infiltration into the lower dermis
and sub-cutis.
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