The American thinker Oliver Wendell Holmes famously quipped that 'history is just one damn thing after another'. 

To the surgical pathologist, his daily diagnostic task may sometimes appear as 'one damn slide after another'.

But such emotions do not do justice to the basics of our profession, and to the analytical potential of our minds. Granted, the neophyte in diagnostic pathology may be overwhelmed by the seemingly endless variation in histological patterns, and be frustrated that for every 'rule' and for every set of 'diagnostic criteria' there are important, and often numerous, 'exceptions'. This is especially true with respect to melanocytic lesions, the diagnosis of which on the one the one hand appears to be deceptively simple (one cell type only; one essential differential diagnosis: naevus versus melanoma), but which has, in the past decades, grown to substantial complexity, with new entities and variants of naevus and melanoma emerging in the literature, and with criteria for already 'existing' entities being modified by new findings and interpretations. The very fact that in some instances, a verdict of benignity or malignancy cannot be made with sufficient certainty, has led to controversial categories such as MELTUMP (melanocytic tumour of uncertain malignant potential) and variants thereof, such as STUMP (Spitz tumour of uncertain malignant potential), and SAMPUS (superficial atypical melanocytic proliferation of uncertain significance). Indeed, the most basic questions - where in the skin does a nevus emerge? What proportion of melanomas arise from a naevus? - have not yet become clear.

Nonetheless, on a sunny morning, we surgical pathologists all realise that much has been achieved (here I do apologize to those whose portraits deserve to be presented here, rather than that of the melanocytologically undeserving O. Wendell Holms), much is now known, and a systemical approach to the histopathologic diagnosis of melanocytic tumors is possible; that we can build on a rational and evidence-based framework of knowledge applicable to day-to-day diagnostics. In the brief introductory texts of this website, I shall outline the essentials and illustrate them with a limited number of 'classical examples' of the most common entities in melanocytic pathology. This will largely be done in the same way as the main part of this website (the Slide Collection), i.e., with virtual slides for self-study, accompanied by brief text remarks, micrographs and some explanatory short films. Hopefully, the visitor of this website will acquire a feeling that the site contains not just 'one damn case after another', but is like a constellation of little stones that, together, form a mosaic that can be interpreted- and to a certain extent understood - and provides a useful basis or adjunct for the diagnosis of melanocytic lesions.