A Curious Case of Pancreatoblastoma in an Older Age Woman

Abstract Introduction/Objective Pancreatoblastoma is a malignant epithelial neoplasm of the pancreas and displays multiple lines of differentiation with acinar differentiation as the predominant pattern. The squamoid nests are considered a defining component of pancreatoblastoma. Pancreatoblastoma is seen most often in children, however, rare cases in adults have been described in the literature. In children, most pancreatoblastomas are indolent and curable, however, the prognosis is worse in adults due to the presence of frequent metastasis. Methods/Case Report We report an interesting case of pancreatoblastoma in a 65-year-old woman with no pertinent medical history who presented with abdominal discomfort. MRI abdomen showed an 11.3 cm mass with central necrosis within the head of the pancreas. Fine-needle aspiration (FNA) of the mass showed monotonous cells with neuroendocrine differentiation and FNA was signed out as a low-grade neuroendocrine tumor (NET). The patient underwent a Whipple resection for a presumed NET. On gross examination, a 14 cm large solid, fleshy, lobulated, partially encapsulated mass was noted in the head of the pancreas. H&E slides on low power showed the tumor composed of highly cellular lobules separated by fibrous bands. Within the lobules, the neoplastic cells predominantly had an acinar differentiation with focal trabecular or solid areas. Dispersed within the tumor were squamoid nests composed of plump to spindle-shaped cells with abundant eosinophilic cytoplasm arranged in whorls. Immunohistochemical stains demonstrated squamoid nests being positive for CK5/6 and had a nuclear-staining pattern with beta-catenin. The remaining tumor was positive for trypsin, chymotrypsin, BCL-10, synaptophysin (focal), chromogranin (focal), and INSM-1 (patchy). On MSK-Impact (next- generation sequencing), a mutation in CTNNB1 was detected. Results (if a Case Study enter NA) NA Conclusion In adults, it is important to consider pancreatoblastoma in the differential diagnoses of solid pancreatic tumors while being cautious not to confuse it with neuroendocrine tumor or acinar cell carcinoma. The presence of squamoid nests is critical for its diagnosis. Making a diagnosis of pancreatoblastoma through FNA or pancreatic biopsy can be exceptionally challenging in cases lacking squamoid nests.