Undifferentiated Carcinoma With Osteoclast-like Giant Cells of the Pancreas Misdiagnosed as a Solid Pseudopapillary Tumor

Abstract

Introduction: Undifferentiated carcinoma of the pancreas with osteoclast-like giant cells (UCPOGC) is a rare, highly malignant neoplasm composed of multinucleated giant cells admixed with mononuclear stromal cells. We report a case of UCPOGC misdiagnosed as a solid pseudopapillary tumor of the pancreas (SPT) based on endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB). Methods: We retrospectively reviewed the medical records of a patient diagnosed for the UCPOGC. Results: A 58-year-old male was admitted to the hospital with abdominal pain. Abdominal CT (Figure 1a) and T1-weighted MRI (Figure 1b) revealed a low attenuated and heterogeneous mass with internal hemorrhage and necrosis in the body of the pancreas measuring 5x5 cm. The laboratory investigations including CEA and CA19-9 were within normal limits. EUS showed a hypoechoic mass with mixed cystic and solid components in the pancreas (Figure 2a) and FNAB showed vascular architectures with pseudopapillary pattern (Figure 2b), numerous neoplastic cells with sheet-like arrangement, several multinucleated giant cells and hemosiderin-pigments. Immunohistochemical stain revealed that the tumor cells were positive for alpha 1-antitrypsin, vimentin, beta-catenin etc. These findings were consistent with SPT with marked degenerative change. A distal pancreatectomy and splenectomy were performed (Figure 2c) and histopathological analysis showed tumor cells consisting of atypical mononuclear cells admixed with abundant osteoclastic giant cells (OGCs) (Figure 2d). The OGCs were positive for CD68 (Figure 2e). Unlike the FNAB findings, the atypical mononuclear cells were positive for cytokeratin (Figure 2f). We finally diagnosed as UCPOGC on histopathologic examination of surgical specimens.Figure 1Figure 2Conclusion: Undifferentiated carcinoma with osteoclast-like giant cells of the pancreas can be misconceived as a SPT on EUS and EUS-FNAB.