Can there be any bad effect of cancer of inverted boob/nipple in boy?

A picture: Worth a thousand words. Nipple inversion means scar/fibrotic tissue is tugging inwardly. Boy or girl, man or woman, this is not normal. Need clinical and mammogram to view what is there. Breast ca not common in "boys" uncommon in men, but this needs to be checked out.

No: If you are born with this, it's a non-problem; many nipples aren't quite symmetric and are partly or fully retracted from birth, and there's no increased cancer risk. If a nipple used to look normal and suddenly becomes inverted, it's worrisome and we'd want to know if there's an underlying mass -- in a reasonably lean man this would be by palpating. Boys have near zero breast cancer risk.