Small Hepatoid Variant of Solid Pseudopapillary Neoplasm of the Pancreas: A Unique Case With Long-term Follow-up

Hepatoid tumors are rare neoplasms that arise outside the liver but exhibit morphological and immunophenotypic features resembling hepatocellular carcinoma. Although hepatoid differentiation sometimes occurs in pancreatic ductal adenocarcinoma, its occurrence in solid pseudopapillary neoplasm (SPN) is exceedingly rare. Consequently, the clinicopathological characteristics and natural history of this variant remain poorly understood. We report a case of a 37-year-old asymptomatic male with a 6 mm solid pancreatic body lesion that was incidentally detected during routine abdominal ultrasonography. Multimodal imaging showed a well-circumscribed solid mass showing early-phase hyperenhancement relative to the surrounding pancreatic parenchyma. Tissue samples obtained via endoscopic ultrasonography contained polygonal epithelioid cells with abundant eosinophilic cytoplasm and a hepatoid appearance. In immunohistochemistry, HepPar-1 and CD10 were diffusely positive, chromogranin A and synaptophysin were absent, and β-catenin accumulated within the nucleus, all supporting a diagnosis of SPN with hepatoid differentiation. Although surgical resection was recommended, the patient declined and was subsequently managed with active surveillance. After 5 years of follow-up, the lesion remained morphologically stable without clinical progression. To our knowledge, this case report is the first to describe the long-term natural course of a pancreatic hepatoid SPN managed nonoperatively. The patient's maintained stability supports the indolent biological behavior of this rare variant. Thus, conservative management with close surveillance may be feasible for carefully selected patients with small, asymptomatic tumors. However, additional cases are needed to clarify optimal management strategies.