Hello

Would it be possible to attach a picture of the potato?

Also, is the one you grew yourself or is it purchased? About how long have you had it in storage?

This information would be very helpful to our expert, so they can help, you. Thank you.

Thanks for the question.  

The picture is probably not clear enough to identify the growth. It may be no more than a sprout or a conjoined tuber that has not yet broken down like the rest of the potato. Cutting the growth in half could provide further information.

I hope this is helpful.

Here is some info (with pictures) of knobby potatoes. These can form for various reasons.

• https://cropwatch.unl.edu/potato/deformations
• https://www.ag.ndsu.edu/publications/crops/potato-tuber-second-growth

It is unlikely that multiple/second growth tubers are a mutation but rather due to environmental influences.  It is possible that they could break off and grow other potatoes. If you could send some well focused pictures we can see what we are dealing with.