Acinar Cystic Transformation of the Pancreas: Report of Three Cases.

Acinar cystic transformation (ACT) of the pancreas is a rare non-neoplastic cystic lesion. It is most frequently observed in the head of the pancreas. Despite advances in radiologic imaging methods, preoperative diagnosis of acinar cystic transformation is difficult, it is often confused with other cystic lesions. Here, we report three cases of acinar cystic transformation, one of which showed diffuse involvement of the pancreas, and the remaining two were multilocular localized cystic lesions. We analyzed their histomorphologic and immunohistochemical features. The patients' ages ranged between 15 and 43 years and the ratio of females to males was 2:1. On microscopic examination, the cysts were lined by a single layer of flattened-cuboidal or columnar epithelial cells. The epithelial cells were diffusely positive with trypsin and keratin 7, but patchy with keratin 19. Due to its rarity and lack of radiologic and clinical awareness compared with other pancreatic cystic lesions, preoperative diagnosis of acinar cystic transformation is difficult and not definitive. All cases reported to date have been clinically benign and there is no evidence of recurrence or malignant transformation. The optimal treatment and whether to perform surgery remain controversial.