Adenosquamous carcinoma of the bile duct: cytologic features of brush specimens from two cases

Cytologic brushing is a safe and specific procedure for diagnosing carcinoma of the distal bile duct and proximal pancreatic duct. The vast majority of these lesions are pure adenocarcinomas. Occasionally, however, other morphologic subtypes may be encountered. We report our experience with two adenosquamous carcinomas of the bile duct diagnosed by cytologic brushing. Both patients presented clinically with jaundice and were found to have mass lesions obstructing the bile duct. The brush specimens were cellular and contained a mixture of glandular and squamous elements. The glandular component was characterized by cohesive aggregates of cells with hyperchromatic, overlapping nuclei. The squamous component contained clusters and individual cells with hyperchromatic oval-to-spindled nuclei and orangeophilic cytoplasm. Focally, the squamous elements appeared to gradually merge into the glandular component, and there were clusters of hybrid cells which were difficult to classify as squamous or glandular. Although uncommon, these 2 cases demonstrate that the cytologic features of adenosquamous carcinoma can be appreciated on cytologic brushing specimens.