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: Endometrial cancers diagnosed in women treated with tamoxifen have poorer prognosis .
### Output Text:
Endometrial cancers diagnosed in women treated with <span class="chemical">tamoxifen</span> have poorer prognosis . 