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: Mapping of homozygous deletions on human chromosome 10q23 has led to the isolation of a candidate tumor suppressor gene , PTEN , that appears to be mutated at considerable frequency in human cancers .
### Output Text:
Mapping of homozygous deletions on human chromosome 10q23 has led to the isolation of a candidate <span class="disease">tumor</span> suppressor gene , PTEN , that appears to be mutated at considerable frequency in human <span class="disease">cancers</span> . 