Comparative cytologic features of pancreatic acinar cell carcinoma and islet cell tumor.

Acinar cell carcinoma (ACC) and islet cell tumor (ICT), both rare pancreatic neoplasms, can be diagnosed accurately and rapidly with the use of imaging-guided fine-needle aspiration biopsies. The specific cytologic features of these tumors are described in a series of 17 patients, and histologic and immunocytochemical correlations are discussed. Important cytologic findings in ACC are loosely cohesive clusters with cells having uniform nuclei and prominent nucleoli, cytoplasm is finely granular and eosinophilic. Islet cell tumors show many single cells, occasional rosettes, uniform nuclei, sometimes binucleate, dense basophilic cytoplasm. Chromogranin is often positive (80%) in ICT. Trypsin and chymotrypsin were often positive (71%) in ACC. Histology was confirmatory in all cytology cases. The recognition of cytologic features in conjunction with immunocytochemical studies can increase the diagnostic sensitivity for these two rare tumors.