My mom 65 yrs old gets big blue black bruises tht don't hurt on legs & thighs without hitting herself anywhere. asthma & mild depression. worrisome?

See doctor: Although bruises may occur with aging skin (from cumulative sun exposure, smoking etc), she needs to see her doctor to get tested. For example, she may have a bleeding disorder which is potentially life-threatening. At the minimum, her platelet count needs be studied.

Yes, this calls for: a trip to your local MD. Bruising as you described is a sx of possible major health conditions that can only be assessed in the doctor's office. The depression also needs to be assessed, either there or at a psychiatrist's office, since there are possible complicating medicals...