Classification and Regression tree for differentiating primary melanoma from metastatic melanoma using Braf, nuclear p300 and cytoplasmic p300 expression. PM, primary melanoma, includes AJCC stages I and II cases. MM, metastatic melanoma, includes stages III and IV. ‘n’ indicates the number of samples and ‘%’ indicates the percentage of samples available at the respective node. Improvement is an indicator of separation achieved by the application of the respective marker to classify the parent node.