The adjuvant prognostic value of nuclear morphometry in stage I malignant melanoma of the skin. A multivariate analysis.

In order to evaluate the adjuvant prognostic value to tumor thickness of other clinical, qualitative histologic and morphometric features, a multivariate analysis was performed in 68 patients with stage I cutaneous malignant melanoma and at least five years of follow-up. Stepwise linear regression analysis confirmed that tumor thickness is the most important prognostic factor; the only additional significant feature was the nuclear correlation coefficient (NCC), which is a measure for the roundness versus ellipsoidicity, regularity and homogeneity of the shape of the nuclei in tissue sections. In general, tumors with ellipsoid (spindle-shaped) nuclei were associated with a better prognosis, even in thick tumors, and tumors with predominantly round nuclei were associated with a poorer prognosis. If the NCC was below 0.94, the prognosis was good irrespective of the tumor thickness: all patients with such a low NCC have survived. Further analysis of this feature showed it to be strongly correlated with the nuclear axes ratio (longest axis divided by the shortest axis). The subtlety of the differences in nuclear shape makes it practically impossible to subjectively detect the significant prognostic level of ellipsoidity, especially in borderline cases. The advantage of the application of morphometry is that it allows the objective description of subjective impressions, and minor shape differences can be detected. The significant adjuvant prognostic value of nuclear morphometry to tumor thickness makes it worthwhile to consider these features together in future prognostic studies concerning malignant melanoma. Furthermore, inclusion of nuclear shape morphometry in clinical pathology reports seems advisable.