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: To define the possible role of the VHL gene in the development of sporadic renal cell carcinomas , 91 different parenchymal tumours of the kidney have been investigated for mutation of the VHL gene by single strand conformation polymorphism ( SSCP ) and / or heteroduplex ( HD ) techniques .
### Output Text:
To define the possible role of the <span class="disease">VHL</span> gene in the development of <span class="disease">sporadic renal cell carcinomas</span> , 91 different <span class="disease">parenchymal tumours of the kidney</span> have been investigated for mutation of the <span class="disease">VHL</span> gene by single strand conformation polymorphism ( SSCP ) and / or heteroduplex ( HD ) techniques . 