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: Genetic heterogeneity in hereditary breast cancer : role of BRCA1 and BRCA2 .
### Output Text:
Genetic heterogeneity in <span class="disease">hereditary breast cancer</span> : role of BRCA1 and BRCA2 . 