Melanoma Classification

Morphological classification

It takes into account the fact that, despite being a single disease, it develops at different times through various stages of progression in which it presents different clinical and histological aspects. Based on the morphology of the lesion we can distinguish a flat melanoma (not palpable and palpable) and a dome-shaped one.

Flat melanoma

It has two clinical aspects that generally follow one another, namely non-palpable flat melanoma and palpable flat melanoma. It appears as an irregularly shaped lesion, usually larger than 6 millimeters in size, which appears to have grown in a centrifugal sense, ie the so-called "horizontal" growth. It is the most frequent variant (80% of cases) and can arise in any skin site but also mucosa. The non-palpable plane is very small if localized to the trunk or to the limbs (macular plane), but can be much larger if localized to the face, in the palpar and plantar regions (soles of hands and feet) and to the mucous membranes (plane in patch). Being in this phase endowed with a modest aggressiveness, its surgical removal, carried out in an adequate way, leads to healing in almost all cases. The ABCDE characteristics can be all present or present only in part. In particular, the "size" criterion (D) may be missing; even if they are sometimes not very evident, there are instead the asymmetry, the irregular edges and the dark brown or blackish color, sometimes irregularly distributed. There are numerous pigmented (colored) lesions that can show morphological characteristics similar to those of non-palpable flat melanoma ; however, the more intense color for melanoma than that of the other nevi present in the same subject, the age of onset, usually more advanced, than that of common nevi and the speed of growth with doubling of size in 6 -8 months of a recent lesion.

The palpable plane appears slightly raised on the cutaneous plane and is therefore "palpable". Its dimensions can be less than one centimeter in diameter (flat papular melanoma) or up to several centimeters (flat plaque melanoma). The ABCDE characteristics described for the non-palpable shape are present, and that is: decidedly asymmetrical shape with bizarre aspects, edges with irregular and indented pattern with "geographical map" aspects, dark brown or blackish color with pink, red or greyish areas unevenly distributed (polychromatism), surface with accentuated or disappeared skin pattern, sometimes with areas of erosion covered by scales or crusts. In this phase we begin to see the phenomenon of spontaneous regression due to an attack by the immune system of the subject against the neoplastic cells, and highlighted by the appearance, in the context of the tumor, of areas of grayish-white color or by the color of the normal skin. Sometimes the regression can be total, but it is in any case an index of poor prognosis because in these cases, very often, metastases are already present in the regional lymph nodes or in other organs and parenchyma.

Dome-shaped melanoma

It is less frequent (about 18% of cases), appears on healthy skin and can be located anywhere (ubiquitous). It tends to grow mainly in height (vertical growth). It appears as a papule (lesion detected by increased thickness of the epidermis, dermis or both) or a nodule (tumor infiltrate in the medium-deep dermis), of regular shape, hemispherical, with a smooth surface, with a brown-blackish or black color. bluish, fleshy, often eroded and bloody and covered with scales and crusts. The boundaries with the surrounding healthy skin are always clear. The ABCDE formula, in this form, is of little use. The pigment can be distributed unevenly until it is completely absent (achromic melanoma). In this case, on careful clinical examination, a blackish shade (pigment leak) of great diagnostic importance can sometimes be identified at the base of the lesion.

Flat-domed melanoma : the onset of a papule or nodule in the context of a palpable or non-palpable flat melanoma is a very frequent event that often occurs even years after the appearance of the primary lesion. It therefore represents the evolution of the neoplasia and more precisely the transition from horizontal to vertical growth.

All clinical variants can be surrounded by satellites: these are small blackish-brown or non-colored tumor nodules that are arranged around the main lesion. Local metastases with lymphatic spread are considered.

Melanocytic nevus-melanoma association

Melanoma can arise on an acquired (which occurs after birth) or congenital (already present at birth) melanocytic nevus. The frequency of this association is estimated around 20-50% of cases.

The possible warning signs of nevus association with melanoma are:

color modification;
sudden appearance of a detected lesion (papule or nodule) in the context or periphery of the nevus;
rapid increase in size and thickness;
erosion or bleeding with subsequent crusting;
signs of inflammation (warmth, swelling, redness, pain);
appearance of subjective symptoms such as itching or stabbing.

Clinical variants in relation to the site

In elderly people, melanoma develops quite often on the face, in a flat form, and evolves very slowly, extending for a long time only superficially until it assumes considerable dimensions over many years (patches or plaques of an uneven brown color with an uneven appearance This form of presentation is still called lentigo maligna. Only late can this form of melanoma become invasive, do they take on the clinical appearance of flat cupoliform melanoma.
On mucous membranes such as the vagina, anus, mouth and oral cavity, upper airways, esophagus and conjunctiva, melanoma generally develops as a single, dome-shaped lesion, often blackish in color, with frequent erosions from the early stages.
In the sub-nail area (below the nail), the neoplasm may initially be confused with a hematoma (blood extravasation) due to trauma. In this case, the evolution of the lesion must be carefully followed: a blood extravasation, albeit slowly, it is eliminated with the growth of the nail because it moves towards the tip of the same, while a melanoma tends to grow slowly and does not grow towards the tip of the nail but can remain localized in place or grow backwards, giving a black and all pigmented at the cuticle of the nail, which in the case of the hematoma remains pink instead.

Natural evolution

A melanoma left to its natural evolution tends to grow irregularly, to ulcerate, sometimes to regress spontaneously and, above all, to metastasize.
Irregular growth is a characteristic feature of all tumor-affected tissues. The same applies to ulceration, linked to an imbalance between the neoplastic mass and its vascularization, resulting in a lack of blood supply and nutrition of the cells. The regression can be partial or total and, when this latter event occurs, the neoplasm often has already metastasized. They can spread by the lymphatic route (through the lymphatic vessels) or by the blood route (through the blood) and can be divided into:

Metastasis satellites, within 5 centimeters of the primary lesion. They are generally visible as pigmented papules;
Metastasis in transit, between the primary lesion and the first lymph node that drains that skin site. They appear as rather hard nodules, sometimes visible and palpable;
Metastasis regional, in the lymph node drainage station. They are highlighted by the enlargement of the lymph nodes which sometimes become even visible and which, on palpation, are hard, painless and mobile;
Metastasis at a distance, in the other organs, above all, in decreasing order of frequency, skin and subcutis, lymph nodes, lungs, liver, brain and bones.

Staging according to the AJCC (American Joint Committee on Cancer)

Stage 0: melanoma in situ;
Stage I: melanoma less than or equal to 1 millimeter with or without ulceration or melanoma between 1 and 2 mm in diameter without ulceration;
Stage II: diameter between 1 and 2 mm with ulceration or greater than 2 mm with or without ulceration but without involvement of the lymph nodes;
Stage III: any tumor thickness with involvement of regional lymph nodes and / or in transit metastases;
Stage IV: distant metastasis.