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 majority of mutant mice rapidly develop thymic lymphomas and die before 4 months of age .
### Output Text:
The majority of mutant mice rapidly develop <span class="disease">thymic lymphomas</span> and die before 4 months of age . 