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

Abstract

Background & Objectives: Gallbladder carcinoma is an aggressive malignancy, with adenocarcinoma being the most
common histological subtype. Adenosquamous carcinoma is a recognized but uncommon variant, while the presence of
small cell neuroendocrine differentiation within adenosquamous carcinoma of the gallbladder is exceedingly rare and
associated with poor prognosis.
Case Presentation: We report the case of a 66-year-old female who presented with right hypochondrial pain and
jaundice. Histopathological examination of a simple cholecystectomy specimen revealed an infiltrating neoplasm
exhibiting glandular architecture, squamoid differentiation, and sheets of small round cells predominantly on the
serosal aspect. Immunohistochemistry showed p63 and CK positivity in squamoid nests and neoplastic glands
respectively, 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 and
aggressive entity. Accurate histopathological evaluation with immunohistochemistry is essential for correct diagnosis
and prognostication.