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: Common to these 71 cases has been a histopathologic diagnosis of focal nodular hyperplasia , adenoma , hamartoma , and hepatoma .
### Output Text:
Common to these 71 cases has been a histopathologic diagnosis of focal nodular hyperplasia , adenoma , hamartoma , and hepatoma . 