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: If the patient develops a liver mass , because of non - specific clinical features and imaging appearances , biopsy may be the only way to achieve a definitive diagnosis .
### Output Text:
If the patient develops a liver mass , because of non - specific clinical features and imaging appearances , biopsy may be the only way to achieve a definitive diagnosis . 