Can bumps under skin on lower legs that itch at first and then harden with discoloration of skin and swelling be signs of cancer?

Unlikely: It is unlikely that these are signs of cancer, but you should make sure that your primary care physician examines you. Depending on what he thinks they are, referral to a dermatologist may be indicated.

Unlikely.: Itching, hardness (medical term induration) and swelling sounds much more like an inflammatory reaction. There are lots of possible causes, but cancer is not likely to be one of them.

See your doc: Any new skin lesions should be brought to the attention of your friendly dermatologist.