Measurement and Figure in Dermatology

To the Editor.—  I read with interest the article by Illig and co-workers¹ on congenital melanocytic nevi and malignant melanoma. Size seems to be an important parameter for the development of melanoma in such nevi. This was also demonstrated by Greely et al,² who stated that nevi with an area of more than 900 sq mm should be considered as potential precursor lesions.Although most of the nevi display a rather simple geometric form such as an oval, the statement of just the largest and smallest diameter is not really satisfying. Instead, I would suggest a very simple procedure that allows rapid determination of the actual area of such lesions.The lesion to be measured is covered by a transparent sheet carrying a lattice or regularly spaced points. According to well-known morphometric principles,³ each point (crossover point) represents an area fraction equal to the whole area divided by