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: Recent work has identified a mouse gene ( tsg101 ) whose inactivation in fibroblasts results in cellular transformation and the ability to produce metastatic tumors in nude mice .
### Output Text:
Recent work has identified a mouse gene ( tsg101 ) whose inactivation in fibroblasts results in cellular transformation and the ability to produce <span class="disease">metastatic tumors</span> in nude mice . 