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: We have reported the presence of a specific mutation ( ATG50 - - > AGG ) or deletion of codon 50 of the ARP gene in different tumor types ( Shridhar et al . , 1996 , 1996a ) .
### Output Text:
We have reported the presence of a specific mutation ( ATG50 - - > AGG ) or deletion of codon 50 of the ARP gene in different <span class="disease">tumor types</span> ( Shridhar et al . , 1996 , 1996a ) . 