SMAD4 and neoplasm: Aside from patients in the high-SPRR1A-expression group being significantly younger than those in the low-SPRR1A-expression group (median age 65 vs. 72 years old, p = 0.022), there was no significant difference in the following variables: gender, body mass index (BMI), carcinoembryonic antigen (CEA), CA19-9, pathological stage, T factor, N factor, histological grade, residual tumor status, peritoneal lavage cytology, neoadjuvant chemotherapy, adjuvant chemotherapy or four major driver mutations of PDAC (KRAS, TP53, CDKN2A/p16 or SMAD4).