Abstract

Duodenal cancer is a rare form of gastrointestinal cancer, accounting for 0.3%-1% of all gastrointestinal cancer incidences. It predominantly occurs in the periampullary sector of the duodenum and is often diagnosed late due to symptomatic manifestations. Hypercalcemia, a condition that can arise from various causes, is often a consequence of osseous metastases or the secretion of paraneoplastic substances like Parathyroid Hormone-related Protein (PTHrP) or 1,25-dihydroxyvitamin D, often in conjunction with compromised renal excretion of calcium. This condition is predominantly linked with oncogenic processes and is infrequently observed in benign pathologies. A case report from the Indian Subcontinent reveals the first instance of primary duodenal adenocarcinoma presenting with hypercalcemia mediated by PTHrP, underlining its exceptional rarity. It is crucial for clinicians to incorporate duodenal adenocarcinoma within the differential diagnostic framework for patients demonstrating duodenal thickening upon upper gastrointestinal endoscopy and hypercalcemia, especially in the face of such rare clinical presentations.