ARTICLE
Cutaneous melanoma (CM) is a potentially lethal neoplasm with a propensity
for distant metastases. Its incidence is increasing and has become a significant
public health problem in many parts of the world [1]. Since the most important
prognostic factor is the thickness of the lesion [2], a successful treatment
directly depends on early diagnosis. An accurate recognition of such pigmented
lesions is therefore very important. But clinicians, who are aware of
this firm and simple cognition have also to consider that both patients
and pigmented skin lesion typology have changed. Public awareness of CM
has increased after extensive media coverage and health education campaigns,
so that patients seek medical advice as soon as they observe a dark lesion
on their skin. Thus physicians often face patients bearing small pigmented
lesions, the differential diagnosis of which must include CM. We have
previously established [3] the frequency of occurrence of small (¾
6 mm) CMs in a clinical context. In that study the value of dermatoscopy
in the diagnosis of those lesions was highlighted in terms of sensitivity.
The aim of the present study was to establish the diagnostic value, in
terms of sensitivity and specificity, of both clinical and dermatoscopic
examinations in a population of patients with unselected consecutive small
pigmented lesions, recruited in a short time.
Patients and methods
Between December 2000 and August 2001, at the Istituto Nazionale Tumori
of Milan 349 patients with 375 cutaneous pigmented lesions that required
surgical biopsy for diagnosis, were consecutively identified in our unit,
all in the same two days of the working week, for the early diagnosis
of melanoma. For all lesions, the decision for diagnostic excision was
based on clinical and/or dermatoscopic features that suggested a more
or less important suspicion for CM. Among these patients, 157 (96 females
and 61 males) showed 161 lesions with a maximum diameter of 6 mm or less.
These lesions are the subject of the present study. The average age of
the patients bearing small lesions was 38 years (range, 14-82). Eighty-eight
(55%) were located on the trunk, 59 (36%) on the limbs, and 14 (9%) on
the head and neck. The sizes of the lesions, obtained with a millimetre
ruler on relaxed skin, ranged from 1 mm to 6 mm in maximum linear extent,
with a median value of 5 mm. The slides were evaluated according to widely
accepted criteria for the histopathologic diagnoses of the various pigmented
lesions [4]. The distribution of the lesions according to the histologic
diagnosis is represented in Table
I. The thickness of the invasive CMs ranged from 0.23 mm to 1.06 mm
(median 0.49 mm).
Two surgical oncologists who are experts in the recognition of pigmented
lesions made, in turn, the clinical diagnoses. Diagnostic criteria were
based on the subjective experience of the single clinician examining the
pigmented lesion, although the ABCD criteria have been the basis of training
at our unit. At present, in practice, we do not consider the ABCD mnemonic
an essential formula for the diagnosis of CM. In fact, our attitude is
not to take into consideration the dimensional character [3], and to attribute
great importance to the colour of a given lesion [5]. A diagnosis of suspect
CM is made when the level of suspicion is roughly 50% or more; lesions
at a lower index of suspicion were considered benign for the purposes
of this study.
Dermatoscopy was performed by the same two physicians who firstly made
and registered the clinical diagnoses. This technique was performed by
a hand-held monocular microscope equipped with an achromatic lens permitting
a magnification of 10x (Heine Delta 10). Dermatoscopic criteria for diagnosis
of malignancy were radial streaming, pseudopods, grey-blue veil, regression
and erythema, whitish veil, black dots at periphery (if network present),
thick irregular network, or milky-red background with red dots. A lesion
was suspected for CM when positive for at least one criterion.
The diagnostic results obtained respectively by naked eye and dermatoscopy
were compared with the histological diagnoses, which have been assumed
to be the correct diagnoses.
Diagnoses were divided into four categories for analysis: true positive,
true negative, false positive, and false negative. Sensitivity is the
proportion of all cases of histologically proven CM that were preoperatively
diagnosed as CM by a given method (clinical or dermatoscopical). Sensitivity
(%) = (true positive x 100)/(true positive + false negative). Specificity
is the proportion of all cases histologically proven not to be CM that
were preoperatively diagnosed as not CM. Specificity (%) = (true negative
x 100)/(true negative + false positive).
Statistical significance of the differences between clinical and dermatoscopic
diagnoses was evaluated by the McNemar chi square test.
Results
The results of the two different diagnostic methods are represented
in Table II and Table
III.
Ten of the 13 CMs were correctly classified using the clinical evaluation,
giving a sensitivity of 77%; 109 of the 148 benign lesions were correctly
diagnosed with the same evaluation, giving a specificity of 74%. Using
dermatoscopy, 10 of the 13 CMs were recognised, with a sensitivity of
77%; 106 of the 148 benign lesions were correctly classified with the
same method giving a specificity of 72%. These differences were not sufficient
to obtain a statistical significance between clinical and dermatoscopic
evaluations (P = 0.74, McNemar chi square test). Combining clinical and
dermatoscopic evaluations all of the 13 CMs were recognised with a resulting
sensitivity of 100%; i.e., the three CMs missed by clinical evaluation
were recognised by dermatoscopy. Conversely, the three CMs misdiagnosed
with dermoscopy were correctly diagnosed with naked eye evaluation. Table
IV shows the presence of the various dermatoscopic major signs used
in our research in the individual melanoma lesions.
Discussion
The ABCD (Asymmetry, Border, Colour, Dimension) criteria for assisting
the visual recognition of early CM were introduced in 1985 [6]. This guide
stipulates that CMs usually are more than 6 mm in diameter. Although a
considerable level of suspicion exists for a pigmented lesion greater
than 6 mm, requiring this feature when using the ABCD may results in some
CMs being falsely classified as benign. Indeed, small melanomas (¾
6 mm), not only exist on clinical grounds, but they also represent a considerable
subset of all CMs [3]. Their clinical features are sufficiently distinctive
to suggest the correct diagnosis from 25 to 62% of the cases [3, 7, 8].
Present data show that up to 77% of small CMs can be suspected clinically.
This value of sensitivity compares well with recent data about CMs of
any size from literature referring results from 70 to 91% [9-13].
Dermatoscopy has been developed as an aid to clinical diagnosis and
its role is well recognised [14-16]. Studies [17, 18] that have included
small doubtful pigmented lesions also suggest that this technique may
be most useful in these circumstances. Recent literature regarding comprehensive
series of pigmented lesions reports a range of 86 to 94% for sensitivity,
and 79 to 81% for specificity in diagnosing CM [19-23]. Our study shows
lower results, giving a sensitivity of 77% and a specificity of 72%. The
reason for this discrepancy might be due to the smaller dimensions of
our lesions that may have made accurate diagnosis more difficult. A small
pigmented lesion may have not yet developed the full spectrum of dermatoscopic
features characteristic of larger lesions, either melanoma or melanocytic
naevus. Also another structured algorithm, such the ABCD rule of dermatoscopy
[21], showed a serious difficulty in managing small melanocytic skin lesions
[24]. Nevertheless, a dermatoscopic sensitivity of 77% can be considered
a not negligible result.
Figures 1 and 2
illustrate a paradigmatic case, in which dermatoscopy
reinforced the decision for a diagnostic biopsy.
In a previous study [3], combining the diagnostic results of both clinical
and dermatoscopic methods, we reached a higher rate of recognition (86%)
of small CMs than when the two methods were considered separately. Findings
of the present study confirm and stress the complementary role of clinical
examination and dermatoscopy. In fact, in combining the two methods, a
correct diagnosis in all the 13 small CMs of our series has been produced.
Although the number of our CMs was small, the possibility of achieving
a sensitivity of 100% is impressive. Other authors stressed the importance
of integrating clinical and dermoscopic examinations in the diagnosis
of pigmented skin lesions [25].
A consideration can be made of the ratio between CMs and pigmented lesions
removed in the present study. Our unit is working in a referral centre,
where a considerable number of early CMs come to observation. Consequently,
there is a strict ratio between CMs and pigmented lesions removed. This
ratio is currently 1:5. The fact that in our series of small lesions this
ratio was 1:12 may reflect both the concern of the clinicians to miss
small CMs in front of a small spot on the skin of their patients, or simply
the fact that the more a lesion is small the more is the diagnostic insecurity
of a clinician.
CONCLUSION
Some conclusions can be drawn from our data. Both clinical and dermatoscopic
features of small CMs appear sufficiently distinctive to suggest the correct
diagnosis in the majority of cases. Clinical examination coupled with
dermatoscopy by experts is the diagnostic cornerstone of small CMs. Clinical
examination remains of utmost importance in diagnosing melanoma. This
consideration must be kept in mind in the current clinical activity of
all the physicians devoted to the early diagnosis of CM. In particular,
this concept must be stressed in the education and training of young dermatologists,
who may have a real risk of underevaluing clinical examination in an era
in which dermatoscopic systems for automated diagnosis have gained many
supporters [26].
Article accepted on 19/8/02
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