Information on the skin biopsy
Selecting the biopsy technique
Partial biopsy of malignant tumours
Depending on the size and site of the tumour,
as well as the degree of confidence in the clinical diagnosis,
a primary excision biopsy is not always sensible. For example,
a large, tough basal-cell carcinoma on the face can simulate
a fibrous birthmark or a ruptured cyst, and a melanoma may
simulate a seborrhoeic keratosis. Primary excision with a
plastic covering of the blemish would in such cases amount
to a treatment error.
For diagnosis confirmation, partial biopsies
may therefore be required; these should be performed as shave
biopsies in the case of superficial tumours, and with the
scalpel or as a spindle biopsy in cases of profound tumours.
This allows a portion of tumour that is as large as possible
in the biopsates, with an amount of surrounding tissue that
is as small as possible. 
Deep
biopsies are indicated if the tumours impress clinically
by being tubercles, and if the lower half of the dermis appears
to be infiltrated (kerato-acanthoma, Merkel-cell carcinoma,
etc.) Profound biopsies are also preferable in regions with
particularly thick epithelium, especially the inner surfaces
of hands and soles of feet, where superficial shave biopsies
frequently record only the horny layer.(2) In the case of
large ulcerated growths, a spindle biopsy from the edge of
the ulcer should be performed, as near to vertical to the
ulcer as possible, including small portions of the ulcer and
surrounding skin.
Shave biopsies are to be recommended in early-stage
epithelial tumours (e.g. Morbus Bowen, solar keratosis). Also
in partial biopsies of malign melanoma, it is a case of recording
as large a superficial tumour portion as possible, since the
changes that are critical for the histo-pathological diagnosis
are to be found in the epithelium (such as melanocytes in
higher layers of epidermis, confluence of joints, differing
shapes and sizes of joints, unclear demarcation of individual
melanocytes at the periphery). If melanoma for diagnosis confirmation
cannot be removed completely, then a
broad
shave biopsy, including the side edge of a tumour,
is indicated. The fear once raised that a partial biopsy could
harm the prognosis of the melanoma has been refuted conclusively
in numerous studies.(13) Nonetheless,
shave
biopsies where there is suspected melanoma should
be carried out only in exceptional circumstances, since assessment
of the overall structure of a pigment-cell tumour is vital
for diagnosis.(2)
In superficial tumours, punch biopsies have
the drawback compared with the shave biopsy that significantly
fewer tumours are recorded for any given volume of biopsy.
Punches
from a pigment-cell tumour are frequently inadequate
for any confident diagnosis. In a retrospective study of 1784
partial biopsies on malign melanoma, there was sufficient
material for a definitive diagnosis in only 32% of punch biopsies,
whereas the figure was 86% in the case of shave biopsies.(21)
In the case of punches taken from the centre of a superficial
basalioma, it even turned out that no tumour was evident at
all, due to the irregular extent and focal regression zones.
Use of the sharp spoon is also contra-indicated in cases of
suspected malignant tumours, due to tissue fragmentation.
Nonetheless, if malignant tumours are curetted, the Stratum
papillare should also be recorded, in order that, for example,
where there are solar keratoses, an invasive growth can in
all probability be ruled out. When using the
sharp
ring curette, this is generally the case.
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