Fig. 1Acinar cell carcinoma (ACC). ACCs are typically large (10 cm), fairly well-circumscribed, soft and fleshy. Less commonly, they can be fibrotic or form cystic masses. Other pancreatic neoplasms that form fleshy masses include well-differentiated pancreatic neuroendocrine tumor, pancreatoblastoma, solid-pseudopapillary neoplasm, and lymphoma.
Fig. 2Acinar cell carcinoma. Neoplastic cells show acinar formations, relative cellular monotony, and foci of necrosis. Thin bands of fibrosis separate islands of neoplastic cells.
Fig. 3Acinar cell carcinoma. Poorly differentiated neoplastic cells with focal acinar formations, large nuclei exhibiting irregular chromatin clumping, size variation, and varying N/C ratios. Many mitotic figures are present, consistent with aggressive growth.
Fig. 4Acinar cell carcinoma. Partially intact tissue fragment with neoplastic cells has moderately hyperchromatic, uniform nuclei and delicate basophilic cytoplasm. A lack of single dispersed cells may help to differentiate this from a pancreatic neuroendocrine tumor (Diff-Quik stain).
Fig. 5Acinar cell carcinoma. Single cells with round to ovoid, centrally- or eccentrically-located nuclei. Some of the neoplastic cells contain entangled cord-like clear areas of unknown significance. A well-differentiated endocrine neoplasm is often a difficult diagnosis to exclude, and all such cases should be immunolabeled before a definitive diagnosis is made (Diff-Quik stain).
Fig. 6Acinar cell carcinoma. Neoplastic cells arranged singly or in groups. There are round to ovoid nuclei with uniform chromatin patterns and delicate, fragile cytoplasm. While these features are typical of acinar cell carcinomas, they may also be present in some well-differentiated pancreatic neuroendocrine tumors (Papanicolaou stain).
Fig. 7Acinar cell carcinoma (ACC). Poorly differentiated ACC. Neoplastic cells are disorganized, but several atypical acinar formations are present. The acinar formations can be easily confused with "rosettes" of an endocrine neoplasm (Papanicolaou stain).
Fig. 8Acinar cell carcinoma. Poorly differentiated neoplastic cells with bizarre, pleomorphic nuclei, macronucleoli, and eosinophilic cytoplasm are observed. Several well-formed intranuclear pseudoinclusions are present. The smear background is characteristically granular.