In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: We report a case of bile duct hamartoma which developed in a patient who had been on long - term danazol treatment .
### Output Text:
We report a case of bile duct hamartoma which developed in a patient who had been on long - term <span class="chemical">danazol</span> treatment . 