To assess the functional effect of the p.D321N mutation on the MAPK pathway, we analyzed the phosphorylation status of ERK1 and ERK2 in primary cell culture from the patient's tumor biopsy compared to healthy control tonsil (from elective tonsillectomy), and also in HEK293 cells transiently transfected with wild-type or p.D321N mutant MAPK1 constructs generated by site-directed mutagenesis. The gene discussed is MAPK3; the disease is neoplasm.