Defying the Prognostic Odds: A Case Report of Unexpected Complete Remission of Metastatic Ampullary Carcinoma With Palliative Chemotherapy.

Metastatic ampullary carcinoma (AC) almost always carries a poor prognosis. We present a remarkable case of a 69-year-old male with Stage IV pancreaticobiliary-type AC who achieved a complete remission after 45 months of palliative modified FOLFIRINOX chemotherapy (5-fluorouracil, oxaliplatin, leucovorin, irinotecan). This unexpected outcome challenges the conventional understanding of the natural history of advanced AC. Furthermore, molecular analysis revealed a pathogenic PALB2 mutation, along with variants of unknown significance in the POLD1 and RAD50 genes, coding for enzymes involved in various deoxyribonucleic acid (DNA) repair pathways. These findings raise questions about their potential influence on treatment response and prognosis. This case underscores the need for further investigation into the role of molecular alterations and personalized approaches in managing advanced AC.