Mechanical hypersensitivity and alterations in cutaneous nerve fibers in a mouse model of skin cancer pain.

Melanoma inoculation induced marked mechanical allodynia and hyperalgesia in the periphery of the melanoma mass in mice from about day 10 post-inoculation. In the middle of the tumor, there were slight hyperalgesia and response disappearance in the early and late phases, respectively. PGP9.5-like immunoreactivities increased in the epidermis of the periphery of the tumor and disappeared from the dermis of the middle on day 18 post-inoculation, without apparent alterations on day 10. When using this pain model, one should consider the tumor site-dependent responses.