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: Cluster analysis showed a random distribution of lesions in the PAN glomeruli in concordance with the random localization of mesangial areas with dysfunction in this model .
### Output Text:
Cluster analysis showed a random distribution of lesions in the <span class="chemical">PAN</span> glomeruli in concordance with the random localization of mesangial areas with dysfunction in this model . 