<s>[INST] my mother is suffering from cancer from last 10 yrs she has taken 28 chemos along with 26 radiaton,now she is suffering from back pain in her L4 -L5 there is harniation grwoeth her left lef is paining due to that  and now from last two days i hv seen a black reddish patch on her right leg,Please will you help in what is that black patch is this any kind of blood clot? [/INST] Hello, such patches can be due to blood clots. This is usually superficial thrombophlebitis. Cancer predisposes to thrombosis. You can check this out either with a clinical encounter with your doctor or with an ultrasound scan which could detect the occluded vessel and the clot. If it is indeed a superficial thrombophlebitis then pain is expected sometimes moderate to severe unless inflammation has already subsided (usually a couple of weeks after the appearance of the patch). I hope I've helped! If you'd like more information, please let me know and I'll be glad to answer. Kind Regards! </s>