Mixed Neuroendocrine and Non-Neuroendocrine Neoplasm of the Gallbladder: Adenosquamous Carcinoma with Small Cell Neuroendocrine Differentiation – A Case Report

Background & Objectives: Gallbladder carcinoma is an aggressive malignancy, with adenocarcinoma being the mostcommon histological subtype. Adenosquamous carcinoma is a recognized but uncommon variant, while the presence ofsmall cell neuroendocrine differentiation within adenosquamous carcinoma of the gallbladder is exceedingly rare andassociated with poor prognosis.Case Presentation: We report the case of a 66-year-old female who presented with right hypochondrial pain andjaundice. Histopathological examination of a simple cholecystectomy specimen revealed an infiltrating neoplasmexhibiting glandular architecture, squamoid differentiation, and sheets of small round cells predominantly on theserosal aspect. Immunohistochemistry showed p63 and CK positivity in squamoid nests and neoplastic glandsrespectively, and synaptophysin positivity in the small cell component, confirming neuroendocrine differentiation.The tumor perforated the serosa (pT3), with perineural invasion present and serosal margin involvement.Conclusion: Adenosquamous carcinoma of the gallbladder with small cell neuroendocrine differentiation is a rare andaggressive entity. Accurate histopathological evaluation with immunohistochemistry is essential for correct diagnosisand prognostication.