New insights into naevoid melanomas: a clinico-pathological reassessment

Abstract

Aims

Because the term 'naevoid melanoma' has variable clinical and pathologic interpretations, we aimed to clarify the features of melanomas referred to as naevoid.

Methods and Results

A review was undertaken of 102 melanomas diagnosed histopathologically as naevoid melanomas and ascertained by European Organisation for Research and Treatment of Cancer Melanoma Group Subcommittee pathologists from their records. We found these could be classified morphologically into 3 groups. Thirteen melanomas were overlying genuine naevi and were therefore excluded. Of the 89 melanomas considered to be naevoid, 11 presented clinically as exophytic papillomatous nodules with little junctional component and composed of small atypical cells showing numerous mitoses and no change with depth; we termed these "papillomatous naevoid" melanomas. The other 78 were flat or only slightly raised and had a superficial spreading melanoma (SSM)-like component with maturation to a small cell, but still atypical, dermal component; we termed these "maturing naevoid" melanomas. We showed that papillomatous and maturing naevoid melanomas also have differing immunochemical profiles. Preliminary clinical follow-up suggested different outcomes for these two naevoid melanoma types.

Conclusions

Melanomas that have been classified as naevoid melanomas comprise two types with distinct clinical, histopathologic and immunohistochemical features that may also be prognostically significant.

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