In fact, at the onset, M is characterized by a non-tumorigenic radial growth phase (RGP), inside the epidermis (intraepidermal) or within the papillary dermis (microinvasive), devoid of metastatic potential, which may be followed, early or late, by a tumorigenic vertical growth phase
(VGP), with deeper extension in the dermis or beyond, nodular confluence, mitotic activity, and metastatic capacity (Table 1).
NMs are the most aggressive subtype with early evolution into the vertical growth phase
It consists of an initial phase that is characterised by radial growth followed by a vertical growth phase
that includes invasion of underlying tissue. Westbury described a clinical classification, which includes: 1- Presence of only primary tumour, 2- Presence of metastasis which includes, 2a- Involvement of adjacent skin, 2b- Involvement of adjacent lymph nodes, 2ab- Involvement of both adjacent skin and lymph nodes. On microscopy, melanoma presents with giant epithelioid cells that are tightly packed with eosinophilic cytoplasm.
For example, tumor ulceration was associated with a 2.85-fold increased risk, male gender had a 1.8-fold risk, a vertical growth phase
tumor had a 7.67-fold risk, and the presence of microscopic satellites was associated with a 6.62-fold increased risk of metastasis, noted Dr.
Invasive melanoma shares the same histologic features but invades the dermis or subcutaneous fat (vertical growth phase
PHASES OF TUMOR PROGRESSION: RADIAL AND VERTICAL GROWTH PHASE
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.
Although there was no difference in median thickness between cases from the two countries, there was a difference in the presence of solar elastosis and the percentage of tumors that showed evidence of being in a vertical growth phase
, the investigation found.
Vertical growth phase
(VGP) melanoma, in contrast, is characterized by the essential feature of tumor nodule formation (Figure 1, C).
At this point, it's called "melanoma with competence for metastasis," or the "vertical growth phase
." Indeed, one study demonstrated a gradual rise in neoangiogenesis with the progression of a tumor from benign metanocytic nevi to atypical (dysplastic) nevi, and then to melanoma (Lab.
In their review entitled "Cellular Heterogeneity in Vertical Growth Phase
Melanoma," Alvaro C.
This was consistent with a vertical growth phase
melanoma with a Breslow thickness of 0.8 mm.