In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: The frequency of codon 50 mutation is roughly the same in pancreatic tumors as in the other types of tumors previously examined .
### Output Text:
The frequency of codon 50 mutation is roughly the same in <span class="disease">pancreatic tumors</span> as in the other types of <span class="disease">tumors</span> previously examined . 