<s>[INST] I have a dermatofibroma on my left shoulder blade and my bra strap irritates it daily. It is 1/4 inch, perfectly round, and purplish in color. Do you think I should be concerned about the possibility of it being cancerous? Had a similar one removed from my abdomen a year ago that looked the same as this one and came back as a dermatofibroma. [/INST] Hi, dairy have gone through your question. You may have dermatofibroma protuberance, benign fibrous histiocytoma or malignant fibrous histiocytoma.  You should go for biopsy of that lump.  It will give you exact diagnosis. Then you should take treatment accordingly.  Excision biopsy is the treatment of choice.  Consult your doctor and take treatment accordingly. Hope I have answered your question, if you have doubt then I will be happy to answer. Thanks for using Chat Doctor. Wish you a very good health. </s>