Figure 3. Activation of Hh signaling in human cancer. Following the discovery of Hh signaling activation in Gorlin syndrome, increasing evidence suggests that Hh signaling is frequently activated in human cancer. Based on current findings, we group these cancers into three groups. Group one is associated with Gorlin syndrome, including basal cell carcinomas, medulloblastomas, and rhabdomyosarcomas (in muscle) (in red). Group two includes cancer types with reproducible data of Hh signaling activation from several groups, such as oral cancer and many gastrointestinal cancers (in blue). Group three includes cancer types with limited or variable results from different groups (in black). Several common cancer types are included in group three; further investigation will provide insight as to the significance of Hh signaling in these different types of cancer.