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: Germ - line mutations of the BRCA1 gene are responsible for a substantial proportion of families with multiple cases of early - onset breast and / or ovarian cancer .
### Output Text:
Germ - line mutations of the BRCA1 gene are responsible for a substantial proportion of families with multiple cases of early - onset <span class="disease">breast and / or ovarian cancer</span> . 