COMT and neuroblastoma: To explore these hypotheses, we compared the expression levels of key enzymes involved in CAT metabolism (TH, DBH, DDC, PNMT, COMT, and MAOA) and NV markers in NB and PHEO/PGL in four NB primary tumor datasets and two PHEO/PGL series using the R2: Genomics Analysis and Visualization Platform (http://r2.amc.nl).