Melanoma with thickness of 0.5 mm is melanoma in situ, or stage 0 (cancer cells are found only in the epidermis, the outer layer of the skin).
This stage is the earliest and most curable, and recurrence and subsequent death, after the local treatment, from melanomas 0.5 mm is a very rare event.
The depth of melanoma lesion, also accurately predicted the risk for lymph node metastasis, with deeper tumors being more likely to involve the nodes.
Melanoma depth is most accurate when measured by evaluating the entire tumor via an excisional biopsy, instead punched biopsy, which gives less accurate results.

I have had melanoma as well, Stage 1A .33 mm.

The poster above told you that all .5mm melanomas are "in situ" (Stage 0) that is not correct. Many early Stage 1 tumors that have progressed beyond the epidermis, even slightly, are well below 0.5mm (my .33 mm for example).

Nevertheless, the 10 year survival rate for most studies for a radial growth phase melanoma of less than .75 mm with no regression, ulceration or other negative factors (i.e., high mitotic rate) is very high (depending on the study you look at 95-99%). So you're clearly in the 95-99% range of not having your cancer recur.

Keep in mind those statistics include elderly and immuno-compromised patients so you really don't have much to worry about and I'm sure you'll be fine with such a shallow melanoma. The .5mm however DOES NOT mean that it is an "in situ" lesion.

Hope that helps

Clark Level
The Clark level refers to how deep the tumor has penetrated into the layers of the skin. This system was originally developed by W. H. Clark, MD back in 1966. Clark levels are officially defined as follows:

Level I: confined to the epidermis (top-most layer of skin); called "in situ" melanoma; 100% cure rate at this stage
You have "in situ" or Stage 0. You are lucky you got it early. You will be okay. MandMs know what she is talking about. Be good use sun blocker and don't get too much sun. Jack

100% cure rate if they do a decent margin and get it all out.