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: Although VHL mRNA was expressed in all three germ layers , strong expression was noted in the central nervous system , kidneys , testis and lung .
### Output Text:
Although <span class="disease">VHL</span> mRNA was expressed in all three germ layers , strong expression was noted in the central nervous system , kidneys , testis and lung . 