Adenosquamous Carcinoma of Gallbladder

Comments:
Squamous differentiation in gallbladder carcinomas can show one of many patterns. Approximately 5% of cases show focal squamous differentiation. Pure squamous cell carcinomas are exceedingly rare (<1% of all gallbladder carcinomas). The term adenosquamous carcinoma is applied when >25% of the tumor is composed of squamous elements.

Based on these criteria, the example shown here is an adenosquamous carcinoma. There are glandular elements on the left and well-differentiated squamous clusters with keratinization on the right. Some of the squamous clusters had lumen and an inner lining of glandular epithelium.