AbstractA case of papillary‐cystic tumor (PCT) of the pancreas in a young woman is reported. Fine‐needle aspiration (FNA) was done preoperatively under ultrasound guidance. The aspirate showed numerous delicate papillary fragments, dyscohesive and monomorphic tumor cells with folded nuclear membranes, and foamy macro‐phages. A diagnosis of PCT of the pancreas was made based on clinical, radiologic, and cytologic findings. The patient underwent distal pancreatectomy without complications. The histopathologic examination of the surgical tissue confirmed the diagnosis of PCT of the pancreas. The tumor cells were faintly positive with mucicarmine and periodic acid‐schiff (PAS) stains. Immunocytochemistry using Ki67 monoclonal antibody showed a cycling index of 0.1 percent, supporting the clinical observation of low metastatic and recurrence rates of this rare tumor. DNA analysis of the tumor showed a DNA index of 1.09 (diploid) and an S‐phase fraction of 5.38%. The tumor cells were positive for progestrone receptors (>15 fmol/mg protein) but negative for estrogen receptors (<15 fmol/mg protein). Abundant mitochondria, prominent endoplasmic reticulum and few junctional complexes were noted on electron microscopy. Emphasis is placed on accurate diagnosis based on preoperative FNA cytology in order to maximize cure rates while minimizing surgical risk and complications. © 1994 Wiley