Abstract
We report a rare case of a large, slowly progressive acinar cystic transformation (ACT) of the pancreas with main duct dilation and atrophy of the upstream pancreas. The diagnosis was made through endoscopic ultrasound-guided through-the-needle biopsy and histological identification of cuboidal acinar epithelium and characteristic immunohistochemistry findings. Distal pancreatectomy and splenectomy were performed because of elevated carcinoembryonic antigen levels, atypical cells on biopsy, and an increase in cyst size. Owing to the benign nature of this case, postresection surveillance was not necessary.