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: Many human tumours have length alterations in repetitive sequence elements .
### Output Text:
Many human <span class="disease">tumours</span> have length alterations in repetitive sequence elements . 