The fine-needle aspiration biopsy cytology of pancreatoblastoma.

We describe the clinical, cytological, histological, and immunohistochemical features of primary and metastatic pancreatoblastoma (PBL), a rare primary pancreatic malignancy of both adults and children. An 18-yr-old male patient presented with abdominal pain, weight loss, and diarrhea and had a 9-cm pancreatic mass that was revealed by CT scan. The fine-needle aspiration biopsy (FNAB) smears from the pancreas specimen and the lung metastasis were cellular and were composed of a combination of solid sheets, three-dimensional, loosely cohesive epithelial groups, and primitive spindled mesenchymal tissue with focal cartilage formation. Acinar formations were best appreciated on cell block preparations, and squamoid corpuscles were seen only on cell block. Zymogen granules were demonstrated in a subset of the epithelial cells using periodic-acid Schiff stains with and without diastase and dual acinar-endocrine differentiation was evident using a focused panel of immunohistochemical stains. Acinar-cell carcinoma (ACC) is the most difficult neoplasm to distinguish from PBL, both clinically and cytologically, especially in young children. The key to distinguishing them is to note the presence of squamous corpuscles and/or heterologous elements such as cartilage. Given the increasing utility of FNAB in the investigation of pancreatic masses, it is important for the pathologist to be familiar with the morphological features of this tumor, especially because preoperative diagnosis provides an opportunity for preoperative therapy before resection.