Which of the following statements regarding ductal adenocarcinoma of the pancreas is/are correct?

a. For ductal adenocarcinoma, 60–70% of tumors arise in the head of the gland, 15% in the body, and 10% in the tail, the remainder are diffuse 

c. For ductal adenocarcinomas, tumors of the body and tail are usually larger at the time of diagnosis than those arising in the head of the gland

Sixty to 70% of pancreatic ductal adenocarcinomas occur in the head of the gland. About 15% reside in the body of the gland, another 10% are in the tail, and the remaining 5% to 15% are diffuse. The predilection of pancreatic cancer to develop in the head of the gland is unexplained, but has the practical consequence that tumors in the head are diagnosed earlier because they cause obstructive jaundice whereas tumors in the body and tail tend to be more advanced at the time of symptomatic presentation. Tumors in the body and tail are typically larger at the time of diagnosis (average, 7 to 8 cm) than in the head (average, 4 to 5 cm).