A patient undergoing chemotherapy reports a dry mouth and painful swallowing with diffuse oral soreness. What is the most likely cause?

Mucositis is a common, painful inflammatory/ulcerative complication of chemotherapy (and radiation) affecting the oral and oropharyngeal mucosa, producing soreness and painful swallowing.Other options: It is not 'normal/expected to ignore'; candidiasis can coexist but classically presents with removable white plaques; geographic tongue is benign and not chemo-induced.Key exam takeaway: Painful, diffuse oral soreness during chemo/radiation = mucositis (manage supportively; rule out superimposed candidiasis).