Problems in the histological assessment of melanoma emphasising the importance of the vertical/nodular component

Abstract

A melanoma in vertical growth phase has an expansile-looking nodule in the dermis growing independently of the epidermis; it may or may not cause an elevation of the epidermis. It is likely to have potential for metastasis and therefore should be given priority in diagnostic reports and by tumour registries. Prognostic assessments which might reasonably include mitotic count, the presence of TIL and tumour thickness need only be applied to this nodular/vertical component of melanoma since all earlier forms of melanoma should be cured by local excision. The features of a radial phase melanoma are less important, apart from the presence of regression which may be a guide to the behaviour of any adjacent nodular/vertical component. The minutiae of the other histological features of prenodular phases of melanoma have little if any bearing on an individual's survival although particular patterns may relate to predisposition to melanoma. The distinction between dysplasia and melanoma insitu and the presence of focal or superficial invasion, whilst diagnostically and conceptually challenging, are not particularly important to patient management.