Hi and welcome to HCM.
It doesnt sounds like cancer ,it sounds like dermatologic disease such as psoriasis
, allergic or autoimmune dermatitis
or many other. Cancer should always be ruled out of course so I suggest to visit dematologist and do skin biopsy
. Second cause can be clotting disorder
which causes subcutaneous haematoma which can spread on this way. WIsh you good health.