Skin cancer and the elderly, does melanoma spots grow quickly?

My mil just went through something similar to this a few months ago. All of a sudden a bump appeared on her forearm, it looked like a boil the size of a dime. Within days it started to get bigger about the size of a quarter, so we took her to her primary dr. He thought it was a boil and tried to lance it but no fluid came out, she left with instructions of warm compresses multiple times s day. He told us if it continued to grow she would need to get to a dermatologist for further evaluation.
It did continue to grow and by the following week when she saw the dermatologist it was almost the size of a half dollar. He scheduled a biopsy at the hospital for the following day and said if need be it would be removed at the same time. As it turned out it was malignant and removed at that time. She is fine now, but is lucky it was in such a visible area to be spotted so quickly.
It is important to anyone, at any age, if you notice any sudden changes on your skin to be vigilant and get to a dr quickly. It could be nothing, but better to find out sooner rather than to late.

There are many things that look like melanoma, but it's best to let a dermatologist look at it. Even if it is something that isn't malignant, the dermatologist can remove it to keep it from growing larger. I've seen some people who have large patches of their face covered with seborrheic keratosis. It looks awful, even though it is benign, and I wonder why they don't have it removed.

I believe that rapid growth is one of the indicators that the spot might be malignant. Based on experience from a relative, the spots can also be slow growing.

I wouldn't take a chance; if your father can't get in touch with his dermatologist, I'd make the call and get him in ASAP.

Hopefully it won't be melanoma, but best to find out about this new growth.