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: Histological examination on 9 of 10 mice with such thrombocytopenia showed changes compatible with myelodysplastic syndrome ( MDS ) .
### Output Text:
Histological examination on 9 of 10 mice with such thrombocytopenia showed changes compatible with myelodysplastic syndrome ( MDS ) . 