Supplementary Material for: Non-Metastatic Pure Pancreatic Hepatoid Carcinoma With Genomic and Transcriptomic Analysis: A Case Report

Background: Pancreatic hepatoid carcinoma (PHC) is a rare and poorly characterized malignancy, with approximately 50 reported cases in the literature. Pure pancreatic hepatoid carcinoma, which lacks any features of adenocarcinoma or neuroendocrine differentiation, is a subset of this population and is extremely rare. Data on its management and genomic findings are limited, and further characterization may provide helpful information in caring for these patients. Case Presentation: A 42-year-old female who was found to have a large, well-circumscribed mass in the body of the pancreas with elevated serum alpha-fetoprotein. Imaging demonstrated an 8.5 cm pancreatic lesion with no other disease. Endoscopic ultrasound-guided biopsy revealed a bile-producing carcinoma with morphological and immunohistochemical features consistent with hepatocellular carcinoma. She underwent a subtotal pancreatectomy and splenectomy, and pathologic evaluation confirmed a well-differentiated pure pancreatic hepatoid carcinoma confined to the pancreas. Whole genome and transcriptome analysis showed microsatellite stability, an elevated tumour mutation burden, copy number alterations in Chr19p13.3 and no mutations typically seen in pancreatic ductal adenocarcinoma (PDAC). These findings support the diagnosis of a pure hepatoid carcinoma with clinical, histopathological, and genomic characteristics resembling hepatocellular carcinoma. She remains disease-free at nine months without adjuvant therapy. Conclusion: This case demonstrates further characterization of a rare pancreatic lesion and illustrates the importance of integrated histopathological and genomic analyses in characterizing rare malignancies. Additionally, our findings suggest that pure PHC may be a distinct entity, rather than a variant of PDAC.