According to Dworak and collaborators., TRG can be classified in four grades: TRG 0, with no regression; TRG 1 represents minimal response, with dominant tumor mass, obvious fibrosis and vasculopathy; TRG 2 is characterized by a moderate response with dominant fibrotic changes and a few easy-to-find tumor cells or groups; TRG 3 indicates a near-complete response with few microscopically difficult-to-find tumor cells in fibrotic tissue with or without mucous substance; TRG 4 defines a complete response with no tumor cells and only fibrotic mass or acellular mucin pools (Table 1). Here, MUC5AC is linked to neoplasm.