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: The BRCA1 or BRCA2 status of four families ( 17 % ) could not be determined .
### Output Text:
The BRCA1 or BRCA2 status of four families ( 17 % ) could not be determined . 