This started as a pimple or in grown chest hair the following day it had a red ring around it then this. My best friends husband just passed away and the doctors are saying they don’t know why or what kind of infection this is. He was in his 30’s. He has been fighting brain cancer.
His symptoms may be abnormal blood coagulation caused by brain cancer, which can cause thrombosis. It may also be a rash caused by vasculitis. Coagulation tests, immune tests, and skin biopsies can help further diagnose the cause.
My guess is that it is some kind of yeast infection, since it is pretty common in patients with a weak immune system (e.g., cancer patients). The doctors would surely do not know what it is just by simply looking at it. They need to do tests! Take a swab of that black area and send it to the microbiology lab to culture the yeast!
How about his PLT value? It might be purpura which is a side effect of some cancers. Purpura is commonly caused by thrombocytopenia which is a deficiency in blood platelets. It can cause bleeding and bruising in the dermis.
Does the red ring look like that in the picture?
The picture shows a skin tinea (fungal infection). I do not know why it finally turns black in your friend.