A Case Report Presenting an Undifferentiated Pancreatic Carcinoma with Osteoclastic-Like Giant Cells with an Unusual Indolent Course.

BACKGROUND Undifferentiated pancreatic carcinoma with osteoclast-like giant cells represents less than 1% of pancreatic cancers. Histogenesis and prognosis are still debated. Three subtypes are defined by the World Health Organization: osteoclastic, pleomorphic, and mixed. The differential diagnosis of a pancreatic tumor with giant cells varies from a benign osteoclastoma to an undifferentiated pancreatic carcinoma with osteoclastic-like cells. The specimen should be carefully examined to rule out conventional pancreatic adenocarcinoma even in the presence of the giant cells. CASE REPORT A 77-year-old male was diagnosed with a pancreatic tail tumor with osteoclastic like cells revealed by a biopsy done by echo-endoscopy; the patient was lost to follow up for 24 months before he was admitted to our institute for severe abdominal pain. A computed tomography showed the same lesion without progression. He was operated on using laparoscopic distal pancreatectomy with splenectomy. Pathology analysis revealed the presence of osteoclast-like giant cells without pleomorphic cells. Mutated KRAS on molecular study confirmed the diagnosis of undifferentiated pancreatic carcinoma with osteoclast-like giant cells. The patient was in good performance status and disease-free 19 months after surgery without any sign of progression. CONCLUSIONS Undifferentiated pancreatic carcinoma with osteoclast-like cells has a challenging pathology diagnosis. Molecular and immunostaining are essential to diagnosis. The absence of pleomorphic cells in the present case has classified it into the osteoclastic subtype. Further cases and studies are needed to confirm the heterogeneity of the malignant course between subtypes.