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In most patients with isolated unilateral retinoblastoma , tumor development is initiated by somatic inactivation of both alleles of the RB1 gene .
 Disease: unilateral retinoblastoma; Disease: tumor
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease 
Text: {0} 
Answer:
 Disease: unilateral retinoblastoma; Disease: tumor