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: Women who carry a mutation in the BRCA1 gene ( on chromosome 17q21 ) , have an 80 % risk of breast cancer and a 40 % risk of ovarian cancer by the age of 70 ( ref . 1 ) .
### Output Text:
Women who carry a mutation in the BRCA1 gene ( on chromosome 17q21 ) , have an 80 % risk of <span class="disease">breast cancer</span> and a 40 % risk of <span class="disease">ovarian cancer</span> by the age of 70 ( ref . 1 ) . 