Does Seborrheic keratosis or Melanoma react to chemo creams for pre cancer? (Photo)

Based on your previous history of melanoma I would definitely get the lesion biopsied and would refrain using the cream on areas that it is not intended for.

The “chemo cream” is probably 5 FU cream which works by poisoning rapidly dividing cells which pre-cancerous cells are. Seborrhoeic keratosis is benign and can be shaved off. If this is done they tend to come back after a while. Therefore, if the cream has improved the lesion, I expect it will come back.

Hello, thank you for your question and picture. Unfortunately, it is difficult to assess your concern through the photos provided. I advise you to not treat lesions on your own and see a dermatologist for appropriate diagnosis and treatment options. If you have treated this lesion with the cream you were given and it is not healing appropriately, it changes in size/color/shape, or you continue to have concerns about it being a melanoma, then seeing your dermatologist would be appropriate.
If you have had melanoma in situ in the past, I would also urge you to make sure you are following up with your dermatologist regularly for your full body examinations.