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: We present such a case in a 15 - year - old boy with APL , where recognition of imaging findings played a crucial role in making the diagnosis and facilitated prompt , effective treatment .
### Output Text:
We present such a case in a 15 - year - old boy with APL , where recognition of imaging findings played a crucial role in making the diagnosis and facilitated prompt , effective treatment . 