Abstract
Acinar cell carcinoma (ACC) of the pancreas is a rare tumor, accounting for 1% to 2% of primary pancreatic neoplasms. Because of its rarity and some histologic similarities to neuroendocrine tumors (NETs), it is generally difficult to establish the diagnosis based on small tissue samples such as needle biopsy. Herein, we report two cases of ACC, where the diagnosis was confirmed by endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) biopsy. Both patients were in their 70s. Tumors sizes were 95mm and 56mm, respectively. Both patients were found to have liver metastases at the initial presentation. EUS-FNA biopsy samples consisted of fragmented tumor tissue, where neoplastic cells were arranged in solid and acinar patterns. The cells have round enlarged nuclei and eosinophilic cytoplasm. Both cases were at least focally positive for both neuroendocrine (i.e., synaptophysin) and acinar markers (trypsin). BCL10, a recently identified immunohistochemical marker for ACC, appeared to be diffusely positive in the tumors, leading to the diagnosis of ACC. Given that BCL10 is a highly specific and sensitive marker for pancreatic ACCs, immunohistochemistry for this molecule will help us to diagnose this rare neoplasm by small tissue samples such as EUS-FNA biopsy.
