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: Atm - deficient mice are retarded in growth , do not produce mature sperm , and exhibit severe defects in T cell maturation while going on to develop thymomas .
### Output Text:
Atm - deficient mice are retarded in growth , do not produce mature sperm , and exhibit severe defects in T cell maturation while going on to develop <span class="disease">thymomas</span> . 