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: The histology comprised squamous carcinoma ( 11 ) , adenocarcinoma ( 1 ) , mixed histology ( 2 ) , bronchio - alveolar carcinoma ( 1 ) and large cell undifferentiated carcinoma ( 1 ) .
### Output Text:
The histology comprised squamous carcinoma ( 11 ) , adenocarcinoma ( 1 ) , mixed histology ( 2 ) , bronchio - alveolar carcinoma ( 1 ) and large cell undifferentiated carcinoma ( 1 ) . 