I have white spots on my back and it sometimes
Pityriasis versicolor, not cancerous
Welcome to ask a doctor service
I have gone through your query and reviewed the attached photograph.
It is looking like pityriasis versicolor which is a superficial fungal infection of the skin.
It is not cancerous.
I would recommend you to take anti fungal medicines like capsule itraconazole 100 mg twice daily for 5 days and apply terbinafine cream on the affected area twice daily for 3 weeks.
This should resolve the white spots.
I hope to have answered your query and would be happy to answer any further queries.