An Extremely Rare and Aggressive Case of Undifferentiated Carcinoma With Osteoclast-Like Giant Cells of the Pancreas Presenting as a Paraneoplastic Syndrome: A Case Report and Literature Review.

Undifferentiated carcinoma with osteoclast-like giant cells (UC-OGC) is a rare tumor type of pancreatic cancer. Paraneoplastic syndromes, an idiopathic inflammatory myositis characterized by various skin manifestations (such as dermatomyositis (DM)), cannot be attributed to the primary tumor itself. Here, we report an unusual case of UC-OGC presenting as a paraneoplastic syndrome, the first reported from Saudi Arabia and the Arabian Gulf states. A 49-year-old Eritrean woman with known DM was referred to our hospital with a left-sided pleural effusion. Computed tomography of the abdomen revealed a large necrotic splenic mass (~17 × 12.9 × 18.2 cm). The patient underwent exploratory laparotomy with en bloc resection of the mass (splenectomy, distal pancreatectomy, and partial excision of the left hemidiaphragm). Following a histopathological examination of the mass, UG-OGC of the pancreas, presenting as a paraneoplastic syndrome, was diagnosed. To our knowledge, this case is the first to present a paraneoplastic syndrome associated with UC-OGC. The identification of an exceedingly rare tumor presenting atypically as a paraneoplastic syndrome shows the importance of conducting comprehensive examinations of patients with malignancies, emphasizing the need for more reports of similar cases.