Dermatoscopy is a non-invasive technique producing
high quality pictures of structures below the skin
surface and invisible to the eye. Such structures
are called dermatoscopic structures and have been
found very useful in the analysis of melanocytic pigmented
Continuing development of the technique has enabled
clinicians to view more regions of the skin sub structures
in better detail. This helps in getting more accurate
diagnosis of skin diseases and designing better treatments.
In the study of dermatoscopic skin structures, it
is necessary to be familiar with some technical terms
that describe these structures. Some of the major
structures are listed below.
- Pigment network is a regular honeycomb structure
made of brown and black lines set on a diffused
- Branched streaks are broadened,
branched lines resulting from a broken pigment
- Dots and globules are sharply circumscribed,
oval or round structures of different sizes
of brown, black
or gray colors. Dots are defined as less than
0.1mm in diameter.
- Streaks are light brown
to black linear structures distributed regularly
or irregularly within
or at the edge of a lesion. Some authors call
streaming when they are radially directed
at the lesion edge and pseudopods when they are
at the edge of the lesion.
areas are areas without any dermatoscopic structures.
They are called
blotches when they
are hyperpigmented in brown, black or gray
the pigmentation is reduced they are called
- Milia-like cysts
are white or yellow round areas.
openings are round, oval or irregularly shaped
or brown-black colors.
- Arborizing vessels
are tree-like branching vessels.
- Maple leaf-like
areas are maple shaped brown to blue-gray pigmented
normally at the
Analysis of Pigmented Lesions
The dermatoscopic structures are used to analyse
pigmented lesions. It is a two-step process.
First step: To differentiate melanocytic from nonmelanocytic
In a melanocytic lesion there must be a pigment network,
aggregated globules, branched streaks and homogenous
blue pigmentation. In the absence of these features,
other features present in non-melanocytic lesions
like milia-like cysts, comedo-like openings, arborizing
vessels, maple leaf-like areas or globules should
be looked for.
Second step: To differentiate benign from malignant
Once melanocytic lesions are identified, one of several
methods is used to differentiate benign lesions from
the malignant ones. All use different algorithms.
Pattern analysis: This is the most difficult and
diagnostically the most accurate method. It needs
a detailed qualitative multiple dermoscopic evaluation.
The disadvantage here is that its accuracy depends
greatly on the expertise of the dermatologist. Several
studies have shown that the accuracy of this method
is lower in less trained dermatologists.
ABCD rule: This is a simpler method which uses four
criteria. A stands for symmetry, B for border, C for
color and D for differential structure. Based on various
parameters and formulas scores are assigned to these
criteria and added to get the total. If the total
is less than 4.75 the lesion is probably benign and
if it exceeds 5.45 it is likely to be malignant. Pigmented
lesions with a score between these two figures should
be suspected for melanoma.
The usefulness of this method was proved in a study
on 194 pigmented skin lesions. The results showed
92% sensitivity and 91% specificity.
Seven features for melanoma is an algorithm based
on seven dermoscopic criteria that predicted melanoma.
These are regression-erythema, radial streaming, irregularly
distributed pseudopods, lack of homogeneity, irregular
pigment network and sharp margin at the edge. Scores
are allotted to these features and added up. A total
score of 2 or more is considered malignant and less
than 2 is taken as benign.
Seven point checklist: It is a simplified pattern
analysis suitable for non-experts. The method uses
a seven-point checklist based on features usually
seen in malignant melanoma. The seven-point checklist
is divided into major and minor criteria. The major
criteria get a score of 2 and the minor ones get a
sore of 1 and the total obtained. Melanoma is diagnosed
if the total is equal to or more than 3.
There was doubt, until recently, among dermatologists
about the usefulness of dermatoscopy. Evidence, now
available, proves that dermatoscopy in the hands of
expert dematologists, is superior to the naked eye
in detecting melanoma. But doubts persist about its
place in the wider world of dermatology. In the future,
it is hoped, emerging advanced techniques will be
better able to diagnose malignant melanoma.