These lesions may represent unrecognized melanomas in the
radial growth phase.
1,2) It typically has a relatively long radial growth phase before becoming invasive.
2) It is distinctive from other types of melanoma in that it has a very short (or absent) radial growth phase before vertical growth.
When melanoma invades into dermis, it may still have only
radial growth phase (single cells or small nests without mitotic figures).
The lesions were distinguished by their smaller size, lack of rapid growth, and
radial growth phase hlstopathology.
These lesions do not have a
radial growth phase, as might be expected with something like melanoma.
The
radial growth phase comprises two steps: (a) the melanoma cells are entirely contained in the epidermis and the cancer is in situ (meaning in place), and (b) the invasive
radial growth phase occurs with the melanoma cells barely invading the dermis, but they do not flourish there.
The term
radial growth phase is clinically derived.
From mid-1992 through mid-2009, during which 1,108 patients underwent serial screening, there were no deaths due to melanoma or any other skin cancer, no metastases, and no sentinel node biopsies, since all melanomas were detected while in their
radial growth phase, when their Breslow depth was well under 0.
Shore's screening program lay in the teachings of well-known dermatopathologist Wallace Clark, who asserted that melanomas in their early developmental
radial growth phase almost never metastasize, and that this phase lasts for at least 6 months.
The fundamental concept that applies to the
radial growth phase (RGP) of melanomas is the slow but generally inexorable proliferation of atypical cells in the epidermis, which may or may not be accompanied by migration of single cells or small clusters of cells into the papillary dermis, where they do not proliferate to form a tumor (Figure 1, A and B).
Kashani-Sabet and his coworkers have shown that
radial growth phase melanoma can bypass the vertical growth phase and progress directly to metastasis in a small but clinically meaningful percentage of cases.
