Final diagnosis of the original biopsy:

Malignant melanoma, superficial spreading type, invasive to level II and a measured thickness of 0.5mm arising in association with a compound nevus, margins free but close.

Final comment:

This lesion is indeed a fully evolved malignant melanoma, superficial spreading type, invasive multifocally to 0.5mm. The radical growth phase is composed of prominent melanoma cells both spindle and epithelioid. They are present in very large nests and show focal pagetold spread. There is evidence of a pre-existing nevus at the site. There is no evidence of regression, ulceration or mitoses. Re-excision is recommended with a 1.0cm margin. SOX-10 and HMB45 support the above interpretation.

Positive and negative controls for all immunohistochemical stains and/or special stains prepared by the outside laboratory were reviewed, and they are considered appropriate.

From the NHS website:

Around 7 out of 10 (70%) of all melanomas in the UK are superficial spreading melanomas.

They’re more common in people with pale skin and freckles, and much less common in darker skinned people.

They initially tend to grow outwards rather than downwards, so do not pose a problem.

But if they grow downwards into the deeper layers of skin, they can spread to other parts of the body.

From Melanoma International:

Here is an explanation of terms that may appear in your pathology report:

1. Type: description of the particular variety of melanoma you have—superficial spreading melanoma, lentigo maligna melanoma, nodular melanoma, and so on. The superficial spreading type is the most common.
2. Growth phase: designation that shows whether the melanoma has reached the step where it can grow as a lump below the epidermis. In the radial growth phase, as we have seen, it is unlikely that the cancer has begun to metastasize. With the vertical growth phase, there is at least some chance that the disease has spread elsewhere in the body.
3. Mitotic count or mitosis: measure of how many melanoma cells are dividing below the epidermis. Only in the vertical growth phase do cells divide in the dermis. The higher the mitotic count, the more likely the tumor is to have spread.
4. Tumor-infiltrating lymphocytes: immune system cells (lymphocytes) whose presence in the vertical growth phase are a positive sign. Presumably, lymphocytes show that the immune system has recognized the tumor and is attacking it.
5. Greatest thickness: the Breslow thickness. A measurement of a millimeter or less is considered thin—and means a favorable prognosis.
6. Site: location of the melanoma. Patients with a vertical growth phase melanoma located on an extremity have a relatively more favorable prognosis than those on the trunk or head and neck (a subtlety is that a rare subtype of melanoma that, unless the lesion appears on the palms, on the soles of the feet, or under the nails acts like trunk lesions).
7. Sex: gender of the melanoma patient. For unexplained reasons, women have a better prognosis than men.
8. Regression: An attribute that may be either absent or present in the radial growth phase (which is adjacent to the vertical growth phase). Regression is evidence of destruction (probably by immune factors) of some of the melanoma cells in the radial growth phase. Immunologically mediated regression of this sort is a weakly negative factor.
9. Level of Invasion: the Clark level. Mine was a level IV tumor—that is, the melanoma had penetrated to just above the fatty layer of the skin.
10. Precursor Lesion: Evidence of a pre-existing ordinary, dysplastic, or congenital mole from which the melanoma might have developed. My melanoma came from a dysplastic nevus. Although dysplastic nevi are the most common precursors, common moles and congenital moles may also be culprits. For many melanomas no evidence of a precursor shows up.

So what I’m getting is that I definitely need to have a larger chunk of skin removed, but it probably didn’t get very deep or spread to other areas.

Thank you, Noah for telling me I had to check this out.