Fine needle aspiration cytology of pancreatoblastoma with immunocytochemical and ultrastructural studies.

ABSTRACT

The cytologic features of a pancreatoblastoma (infantile adenocarcinoma), a rare pancreatic neoplasm of childhood, are described. Fine needle aspiration (FNA) under ultrasound guidance produced a hypercellular specimen consisting of numerous oval-to-cuboidal cells that had a moderate amount of granular cytoplasm. Spindle-shaped, elongated and triangular-shaped epithelial cells were also seen, along with smaller cells that had a higher nuclear/cytoplasmic ratio and a denser cytoplasm. In addition, there were abundant fragments of stroma present, including some surrounded by epithelial cells. Immunoperoxidase studies performed on the aspirated material revealed positive staining of the epithelial cells for cytokeratin (AE1/3), including high and low molecular weight cytokeratin, carcinoembryonic antigen, neuron-specific enolase and alpha-1-antitrypsin. Ultrastructural examination demonstrated epithelial cells containing either large electron-dense zymogen granules in the range of 400 nm to 600 nm or small dense neuroendocrine granules measuring from 100 nm to 200 nm. This finding, in concert with the immunocytochemical studies, supported a "blastemal" cell origin with bidirectional differentiation for this unusual pancreatic neoplasm and enabled a specific preoperative diagnosis of pancreatoblastoma to be made. The differential diagnosis of pancreatoblastoma from other pediatric neoplasms involving the pancreas, including neuroendocrine tumors and neoplasms of acinar cell derivation, is presented. We believe that the FNA cytologic findings can lead to a correct diagnosis of pancreatoblastoma, especially when coupled with immunocytochemical and ultrastructural studies performed on the aspirated material.