Use of washing cytology from removed self-expandable metal stents for biliary strictures: a novel cytology method.

Removability is one of the important features of biliary covered self-expandable metal stents (CSEMS). In this study, we evaluated the diagnostic ability of washing cytology of removed CSEMS. For 14 removed CSEMS that had been placed for the biliary strictures (12 malignant, 2 benign), the surface of CSEMS was washed with saline, and pathological examination of the washing liquid as cytology (CSEMS washing cytology) was performed. The specimen sampling rates and sensitivity for malignancy of CSEMS washing cytology were 92.9 % and 41.7 %, respectively. Sensitivity according to the primary disease was 60.0 % for bile duct cancer and 20 % for pancreatic cancer. Sensitivities based on the methods of stent removal were 16.7 % and 66.7 % for removal through the channel of the scope and with the scope, respectively. Therefore, it is possible that sensitivity of CSEMS washing cytology is higher in bile duct cancer and for removal with the scope. In conclusion, CSEMS washing cytology may have potential as a pathological diagnostic method.