Malignant melanoma associated with a blue naevus: a case report
© Mellone et al; licensee BioMed Central Ltd. 2008
Received: 13 December 2008
Accepted: 31 December 2008
Published: 31 December 2008
Combined malignant naevi are characterised pathologically by the association of a melanoma with one or more different types of benign melanocytic naevi in a single lesion.
We show here a case of malignant combined naevus made up of a blue naevus and a melanoma, presenting as a slowly progressing and asymptomatic pigmented lesion on the trunk of a 35-year-old man. Dermoscopic examination was not conclusive for a malignant lesion, showing only an atypical brown pigment network. The definitive diagnosis was reached only at the hystopathological examination.
This finding suggests that combined naevi should be always excised and histologically examined to achieve a correct diagnosis and avoid risk of misclassification.
Combined naevi are unusual pigmented skin lesions that represent less than 1% of all biopsed melanocytic naevi . They are characterised by the presence of two or more different types of melanocytic naevi in a single lesion, being the association of a blue nevus with a Clark or Spitz nevus the most common entity. Dermoscopic analysis of combined naevi commonly shows a multicomponent pattern with the typical findings of each lesion . However, in several cases, the differential diagnosis between a benign combined naevus and melanoma can be very difficult at the dermoscopic evaluation .
The clinical and pathological significance of melanocytic naevi lies principally in their relationship with melanoma. In the case of combined naevi the problem of a correct diagnosis is complicated by the presence of two or more different types of melanocytic naevi in a single lesion . Overall, at dermoscopic examination naevus-associated melanomas display a lower number of features than de novo melanomas and are also less specific for malignancy . This could be due to the incomplete vision of the neoplastic structures, partially obscured by the associated benign naevi. In the case presented, at dermoscopic examination only an atypical pigment network, feature present also in atypical benign naevi, was detectable with no areas of regression. The histopathological analysis, indeed, revealed that the melanoma was in a early phase of growth and this could account for the absence of regression areas at the dermoscopic examination. In conclusion, dermatologists should be aware that dermoscopic examination of combined naevi could not be exhaustive enough in order to exclude a diagnosis of malignancy. Therefore, these lesions should be always excised and histologically examined to achieve a conclusive diagnosis.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
This work was supported by a grant from FUTURA-onlus to AB.
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