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: Two cases of postinfarction ventricular septal rupture in patients on long - term steroid therapy are presented and the favourable outcome in both cases described .
### Output Text:
Two cases of postinfarction ventricular septal rupture in patients on long - term <span class="chemical">steroid</span> therapy are presented and the favourable outcome in both cases described . 