Can bruising on the calf muscle be bone cancer?

Unlikely: Primary bone cancer is quite rare. Even if you had metastatic cancer to the leg, you would be expected to have significant bony pain long before there would be any soft tissue involvement such as bruising. If you have frequent bruising, see a physician for evaluation of a bleeding disorder.

Usually not: A bruise is most commonly due to tissue injury as the result of trauma, less likely tumor. If there is pain, i would see your doctor.

Is it bruised: If its really a bruise like you hit it. That is not cancer. If you have a hard knot in the muscle, it is unlikely to be cancer but can be things that your regular doctor can help you with.