Hello Welcome to HCM. I hope you are feeling better with chemo. As for the black spots, pigmentation is a common side effect due to the chemo drugs as skin cells also are affected during treatment. The pigmentation may slowly fade away once treatment is stopped depending on the duration of treatment, drugs used,etc. Some maybe permanent. At the moment keep your skin moisturised and sun protected. You can try using a kojic acid gel on the spots, with aloe vera gel. It is better not to use anything stronger along with your chemo. Once the chemo is complete, visit a dermatologist to assess the extent and best treatment for you.