micro melanoma detection.pdf - SASSiT

CLINICAL AND LABORATORY INVESTIGATIONS
DOI 10.1111/j.1365-2133.2006.07396.x
Micro-melanoma detection: a clinical study on 206
consecutive cases of pigmented skin lesions with a
diameter £ 3 mm
A. Bono, E. Tolomio, S. Trincone, C. Bartoli,* S. Tomatis, A. Carboneà and M. Santinami
Melanoma and Sarcoma Unit, *Day Surgery Unit, Health Physics Unit, àUnit of Pathology, Istituto Nazionale per lo Studio e la Cura dei Tumori,
Via Venezian 1, 20133, Milan, Italy
Summary
Correspondence
Aldo Bono.
E-mail: aldo.bono@istitutotumori.mi.it
Accepted for publication
28 February 2006
Key words
dermoscopy, diagnosis, melanoma, micromelanoma,
small melanoma
Conflicts of interest
None declared.
Background Very small pigmented lesions may represent an important diagnostic
challenge to the clinician.
Objectives The aim of the present study was to establish the diagnostic value, in
terms of sensitivity and specificity, of both clinical and dermoscopic examinations
in a population of patients with unselected consecutive pigmented lesions with a
maximum clinical diameter of 3 mm.
Patients and methods Two hundred and four consecutive patients bearing 206 pigmented
skin lesions with a maximum diameter of 3 mm were seen and operated
on. Twenty-three of these lesions were melanomas. Each lesion was subjected to
both clinical and dermoscopic evaluation before surgery. The results were
expressed in terms of sensitivity and specificity of both kinds of evaluation.
Results Clinical evaluation produced a diagnostic sensitivity of 43% and a specificity
of 91%. Dermoscopy resulted in a sensitivity of 83% and in a specificity of
69%. The comparison between the sensitivity values of the two diagnostic methods
showed a significant difference (P

Micro-melanoma detection, A. Bono et al. 571
with a millimetre ruler on relaxed skin, ranged from 1 to
3 mm in maximum linear extent, with a median value of
2 mm. The slides were evaluated according to widely accepted
criteria for the histopathological diagnosis of the various pigmented
lesions. 4 The distribution of the lesions according to
the histopathological diagnosis is represented in Table 1.
Twenty-three of these lesions were CMs (four in situ and 19
invasive lesions). The histopathological subtype of these
tumours was superficial spreading melanoma in 21 cases and
nodular melanoma in the remaining two cases. The thickness
of the invasive CMs ranged from 0Æ2 to 1Æ08 mm (median
0Æ35 mm).
Naked-eye diagnosis was based on the subjective experience
of the single clinician examining the pigmented lesion,
although the ABCD (asymmetry, border, colour, dimension)
criteria have been the basis of training at our unit. At present,
in practice, we do not consider the ABCD mnemonic to be an
essential formula for the diagnosis of CM. In fact, our attitude
is to not take into consideration the dimensional character, 5
and to attribute great importance to the colour of a given
lesion. 6 A diagnosis of suspicious CM is made when the level
of suspicion is roughly 50% or more; lesions at a lower index
of suspicion were considered not CM in the estimate of the
data in this study.
Dermoscopy was performed with a hand-held monocular
microscope equipped with an achromatic lens permitting a
magnification of 10 · (Heine Delta 20 microscope; Heine Ltd,
Herrsching, Germany). Dermoscopic criteria for diagnosis of
malignancy were those of Menzies et al. 7,8
The diagnostic results obtained by the naked eye and dermoscopy
were compared with the histopathological diagnoses,
which have been assumed to be the correct diagnoses. Diagnostic
classification was expressed as sensitivity (i.e. the fraction
of correctly classified CMs), and specificity (i.e. the
fraction of correctly classified nonmelanoma lesions).
Table 2 Distribution of CM and non-CM (206 lesions): clinical
evaluation and dermoscopy
Results
Histopathologically
melanoma
(n ¼ 23)
Histopathologically
nonmelanoma
(n ¼ 183)
Clinical diagnosis
Melanoma 10 16
Nonmelanoma 13 167
Dermoscopy
Melanoma 19 57
Nonmelanoma 4 126
CM, cutaneous melanoma.
The results of the two different diagnostic methods are represented
in Table 2. Ten of the 23 CMs were correctly classified
using the clinical evaluation, giving a sensitivity of
43%; 167 of the 183 benign lesions were correctly diagnosed
with the same evaluation, giving a specificity of
91%. Using dermoscopy, 19 of the 23 CMs were recognized,
with a sensitivity of 83%; 126 of the 183 benign
lesions were correctly classified with the same method giving
a specificity of 69%. The comparison between the sensitivity
values of the two diagnostic methods showed a
significant difference (P

572 Micro-melanoma detection, A. Bono et al.
Fig 2. Dermoscopy of the same lesion as in Figure 1, showing
pseudopods and blue veil.
usually are > 6 mm in diameter. Although a considerable level
of suspicion exists for a pigmented lesion > 6 mm, requiring
this feature when using the ABCD criteria may result in some
CMs being falsely classified as benign. Indeed, small melanomas
(£ 6 mm) exist not only on clinical grounds, they also
represent a considerable subset of all CMs. 5 Their clinical
features are sufficiently distinctive to suggest the correct
diagnosis in 25–62% of cases. 5,10,11 Present and previously
reported 3 data show that 43–45% of very small (£ 3 mm)
CMs can be suspected clinically. Data about CMs of any size
from the literature indicate sensitivity results from 70% to
91%. 12–16 The reason for this discrepancy might be due to the
smaller dimension of our lesions, which may have made accurate
diagnosis more difficult. A very small CM may not yet
have developed the full spectrum of clinical features characteristic
of larger lesions of the same nature. This difficulty in
diagnosing small CMs was highlighted also in managing such
lesions with instruments aiming to an automated detection. 17
Dermoscopy has been developed as an aid to clinical diagnosis,
and its role is well recognized. 18,19 The conventional
dermoscopic diagnosis is based on the assessment of specific
criteria and on the application of different diagnostic algorithms,
the classical pattern analysis put forth by Pehamberger
et al., 20 the ABCD rule of Nachbar et al., 21 the method of Menzies
et al., 8 and the seven-point check list of Argenziano et
al., 22 to name the most relevant ones. Its use increases diagnostic
accuracy between 5% and 30% over clinical examination,
depending on the type of lesion and experience of the
physician. 7,18,23–28 Studies that have included small doubtful
pigmented lesions also suggest that this technique may be
most useful in these circumstances. 5,24,28,29 Literature regarding
comprehensive series of pigmented lesions reports a range
of 68% to 94% for sensitivity, and 78% to 94% for specificity
in diagnosing CM. 21,24,25,30–34 The sensitivity result from our
study (83%) is in line with these data, stressing the usefulness
of the technique also in very small CMs. The lower value of
specificity (69%) in our study may be because all the microlesions
were difficult-to-diagnose ones. This fact might be in
relation to the particular histopathological types of our lesions,
with a prevalence of junctional naevi. However, our specificity
result compares well with the corresponding values reported
in the literature with the method of Menzies et al. 7,8 On the
contrary, another structured algorithm, such the ABCD rule of
dermoscopy, showed a serious difficulty in managing small
melanocytic lesions. 35 However, our data must be discussed
by taking into account the retrospective nature of the study.
In particular, we had not recorded data to establish which
lesions were already planned for excision solely on the basis
of the naked-eye evaluation. In fact, the clinical threshold of
suspicion recorded in our clinical form does not coincide with
a yes/no decision for biopsy. So, the ‘decisional power’ of the
naked-eye evaluation may be higher than one can consider.
This concept is in line with the results of a previous randomized
study on the matter. 36
A point of discussion in our study could be the assumption
of the histopathological diagnosis as the correct one, because
in the literature this type of diagnosis shows growing limitations.
37
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 very small lesions this ratio was 1 : 9 may reflect
both the concern of the clinicians to miss a CM in front of
a small spot on the skin of their patients, or simply the
fact that the smaller a lesion is the greater is the diagnostic
insecurity of a clinician. However, this ‘number needed to
treat’ 38 can be considered satisfactory. In a large series there
was reported a benign to melanoma ratio of 12 for dermatologists
in selected areas of Australia compared with 30 for
primary care physicians. 39
Data from a previous study 3 suggest that micro-melanomas
may represent the earliest clinical manifestation of a melanocytic
malignant neoplasm. In contrast with previous thinking,
40 many of these new-born lesions are unfortunately
already invasive. 3 Although thin, these lesions are on the way
to being life-threatening for the patients. For such reason their
recognition is of the utmost importance.
In conclusion, detection of very small CMs is feasible by
accurate visual inspection. Dermoscopy appears to be an
important aid to the diagnosis, provided that physicians are
aware of this type of lesion and maintain the index of suspicion
at a high level.
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Ó 2006 The Authors
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