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 losses invariably involved the wild type allele derived from the unaffected parent , suggesting the inactivation of a tumor suppressor gene in this region
### Output Text:
The losses invariably involved the wild type allele derived from the unaffected parent , suggesting the inactivation of a <span class="disease">tumor</span> suppressor gene in this region 