Exocrine Pancreatic Neoplasms of Nonductal Origin: Acinar Cell Carcinoma, Pancreatoblastoma, and Solid-Pseudopapillary Neoplasm.

This review describes the clinicopathologic characteristics, differential diagnosis, and biologic behavior of exocrine pancreatic tumors of predominantly nonductal differentiation: acinar cell carcinoma, pancreatoblastoma, and solid-pseudopapillary neoplasm. Patients usually present with a well-demarcated, large, soft, solitary mass with expansile, rather than infiltrative, growth pattern. Cystic change is common. Histologically, the tumors usually reveal at least a focal solid, cellular appearance composed of uniform, monomorphic epithelial cells. However, each type has characteristic clinicopathological features. The immunohistochemical labeling profile of pancreatoblastoma parallels the multiple lines of differentiation. These tumors are capable of producing metastases; however, their behavior is different among the types and even in the same type. Therefore, establishment of a grading system that can predict the outcome would be helpful.