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: Individuals who inherit one mutant allele are at increased risk for breast cancer , and the tumours they develop lose the wild - type allele by heterozygous deletion .
### Output Text:
Individuals who inherit one mutant allele are at increased risk for <span class="disease">breast cancer</span> , and the <span class="disease">tumours</span> they develop lose the wild - type allele by heterozygous deletion . 