Mucinous adenocarcinoma of gallbladder: Subcategorisation on fine-needle aspiration cytology

Background Mucinous adenocarcinoma (MC) of gallbladder is a rare histological subtype of gallbladder carcinoma (CaGB) which presents at an advanced stage and is associated with a poor prognosis compared to the conventional CaGB. This variant has been described mostly as reports or series, except for a single detailed histological and immunohistochemical analysis. Till date, there are no studies describing the cytomorphology of MC in detail. Hence, we undertook this study to analyse the cytomorphological features of MC. Methods A retrospective cytomorphological analysis was performed on MC identified out of all CaGB diagnosed on cytology over a period of last 4 years. The architectural and cellular features were recorded in a structured proforma. Results Thirty-three cases (33/987, 3.3%) were identified as MC. Extracellular mucin >90% was seen only in 3 cases whereas the remaining 30 had 50%-90% mucin. The predominant architectural pattern was tight epithelial fragments (14/33). The tumour cells were mostly of intermediate size (31/33) and had moderate amount of cytoplasm (31/33). Majority of the cases showed moderate nuclear pleomorphism (28/33) and nuclear chromatin was fine granular (17/33) or vesicular (14/33). Most of the cases had single and small nucleoli (26/33). Presence of inflammation composed predominantly of polymorphs was noted in 25 cases. Majority of the cases showed no (15/33) or scant necrosis (13/33). Conclusion The morphological features of MC can very well be demonstrated on cytology. As they are associated with poor prognosis compared to conventional CaGB, cytopathologists should try to document the subtype.