Pancreatic metastases from small cell lung cancer: Systematic review of clinical presentation, diagnosis, and outcomes.

656 Background: Small cell lung cancer (SCLC) is an aggressive neuroendocrine malignancy with frequent metastasis to the liver, brain, and bone. Pancreatic involvement is rare but clinically important, as it may mimic primary pancreatic adenocarcinoma. Distinguishing these is extremely critical, as misdiagnosis may delay systemic therapy or lead to unnecessary surgical intervention. Methods: A systematic review was conducted in accordance with PRISMA 2020 guidelines (PubMed and Google Scholar). Eligible studies included adults with radiologic, cytologic, or histological confirmation of pancreatic metastasis from SCLC, that reported clinical presentation, diagnostics, treatment, and outcomes. Studies without English translation, non-pulmonary primaries, and abstracts without full text were excluded. Data were synthesized qualitatively due to heterogeneous reporting. Results: A total of 47 were identified (mean age 60 years, 77% male). In 57%, pancreatic metastasis was the initial presentation of SCLC. Common symptoms included abdominal pain (66%), weight loss (32%), jaundice (25%), and respiratory symptoms (25%). Mean lesion size was 31 mm, with the pancreatic head most often affected. CT abdomen was the most common initial diagnostic modality, while EUS-FNA provided confirmatory diagnosis in most cases. Immunohistochemistry (IHC) consistently supported pulmonary origin with TTF-1, synaptophysin, and chromogranin positivity. Management was predominantly palliative. Platinum-etoposide was the most common systemic regimen, while ERCP with stenting was frequently used for biliary decompression. Surgery was rarely performed (3 patients). Overall prognosis was poor, with median survival of 9 months, and only two cases achieved complete remission. Conclusions: Pancreatic metastasis from SCLC was predominantly seen in older male smokers and presented with abdominal pain, jaundice, or acute pancreatitis. Accurate diagnosis requires EUS-FNA or CT guided biopsy with IHC, which is essential to differentiate from primary pancreatic adenocarcinoma and avoid unnecessary surgery. Systemic therapy with platinum-etoposide remains the cornerstone of treatment, with endoscopic stenting for palliation. Surgery has little role once metastasis is confirmed. Prognosis remains poor, underscoring the need for early recognition and integration of novel systemic therapies in future trials.