Fig. 13. Granular cell tumor in an asymptomatic 58-year-old female.

A mass lesion in the cystic duct was found on ultrasonography during an annual medical checkup. Laboratory test results, including tumor markers, were negative.

A. Portal venous phase computed tomography shows a thickened cystic duct wall with prolonged enhancement (arrow). B. Open cholecystectomy was performed, and microscopic pathology (hematoxylin and eosin stain, × 200) reveals that the mass contains dense proliferation of polygonal atypical cells with eosinophilic granules (arrowheads). These cells are weakly positive for the Periodic acid-Schiff stain and broadly positive for the S100 stain (not shown).