Survey data show that the average delay in diagnosis of malignant melanoma in clinical practice is 11.1 months, of which 9.8 months are attributable to the patient and 1.3 months to the physician. Early detection of patients resulting in treatment of early limited melanoma results in a long-term survival rate of 92%, while the long-term survival rate of metastatic MM is less than 5%; therefore, prevention and early detection and treatment are essential to reduce the mortality rate of MM.
Risk factors .
Sun exposure: An important factor in the development of melanoma is excessive UV exposure and cumulative exposure time to sunlight. Light-colored skin is at greater risk of developing melanoma than dark-colored skin. Animal studies have shown that UVA and UVB play the same role in the malignant transformation of melanocytes.
Race: Caucasians have a high incidence, Blacks and Asians have less, their lesions are mainly on the extremities, and their prognosis is poor.
Skin type: photosensitive type I skin is prone to occur, tanning-prone type IV has a low incidence.
Age: Melanoma often occurs in adults and occasionally in children. When it occurs in children and young adults, it is often associated with genetic factors such as pigmented dry skin disease, congenital nevus of the trunk, familial dysplastic nevus syndrome, or familial melanoma.
Trauma: The association between trauma and melanoma is minimal in white people and is rarely mentioned or even suspected in the literature. Melanoma in people of color occurs mainly in the extremities, and many extremity melanomas have a very clear causal relationship with trauma.
Patients with melanoma in the family: Patients with a family history of melanoma are also at increased risk, especially if they have multiple nevi. In addition, patients who have had one melanoma have an increased risk of developing a second primary melanoma.
Number, size and type of pigmented nevi.
Congenital nevi are nevus pigmentosus nevi that appear at birth with a 1% neonatal occurrence rate. Most are small, single lesions and large ones (>10M in diameter) are less common. Most studies have shown that congenital giant nevi are the main risk factor for melanoma in congenital nevi. The average rate of malignancy in congenital giant nevi reported abroad is 10%, and about 60% of malignant lesions occur within 10 years of age, so they are considered precancerous lesions of MM. More than 2/3 of congenital nevi have junctional activities, which are more likely to become malignant than acquired nevi.
Clark’s nevus: It is the most common congenital nevus in Caucasians and rare in Yellow. They occur on the trunk, are mostly larger than 1 cm in diameter, are flat patches or nodules, and have mixed colors and irregular edges. All individuals with dysplastic nevi are at increased risk for melanoma, and dysplastic nevi of the extremities and mucous membranes, even if only one is present. The greater the overlap between personal history of dysplastic nevus, family history of dysplastic nevus, personal history of melanoma, and family history of melanoma, the higher the risk.
The number of most pigmented nevi can be used to assess the risk of melanoma development. Having 12 nevi ≥5L in diameter increases the risk 10-fold; having 5 or more nevi ≥7L in diameter increases the risk 16-fold; and having 50 or more nevi ≥2L in diameter increases the risk 64-fold.
The known symptoms of melanoma for clinicians are summarized in the “ABCDEF” diagnostic criteria.
A(asymmetry) shape asymmetry;
B(border irregularity) margin irregularity;
C(color variegation) color is mixed, the damage may be brown, black, gray or white mixed with each other;
D(diameter) diameter ≥ 6L;
E(elevation) elevation; (evolutionary changes) including changes in color, size, symmetry, surface features, pruritus painful bleeding pressure pain;
F(funny-looking)
Usually the conditions for histological diagnosis of malignant black are.
1, tumor cell heterogeneity, which is mainly nuclear enlargement, deep staining, cells and nuclei morphology of different sizes, is the most important indication of malignancy;
2, malignant junctional changes or junctional active: melanocytes or nevus cells at the epidermal-dermal junction show atypical hyperplasia, the cells are scattered and not nested, the nests are of different sizes, or the nests are fused with nests, and there is continuous hyperplasia of heteromorphic melanocytes in the basal layer between epidermal protrusions;
3. The heteromorphic melanocytes are scattered throughout the epidermis, indicating that the lesion is still in the in situ stage;
4. The anomalous nevus cells or melanocytes break through the basement membrane band to invade the dermis. That is, vertical growth or invasive growth;
5. Except for Spitz nevus (juvenile melanoma), the nuclear division of nevus cells can not be seen in the deep dermis, which is often a symbol of malignancy;
6. Lack of maturation phenomenon: usually the nevus cells in pigmented nevus gradually become smaller and longer from superficial to deep dermis, and become small pyknotic cells with solid nuclei, which is called cell maturation, but in malignant nevus, this phenomenon is lacking.
7.Melanin formation increases, so many melanin can be seen in malignant nevus lesions, but in anaplastic malignant nevus (AMM), there is little or no melanin;
8, ulcer formation;
9, banded inflammatory infiltrates often appear in the dermis;
10. Interstitial reaction: When special staining was done, more and dense reticular fibers surrounding single dispersed nevus cells were seen in the deeper layers of intracutaneous nevi, while the interstitial reaction in the deeper layers of malignant nevi was less, with only a few reticular fibers surrounding nested neoplastic cells.
Radial growth phase (RGP): called MM in situ; tumor cells are usually confined to the epidermis and expand peripherally within the epidermis, such as invading dermal papillae, usually with only single cells or forming only small nests of melanocytes (no more than 5-10 melanocytes in size and number); in RGP, melanoma mitoses are often seen in the epidermis, but in the In RGP, melanoma mitoses are often seen in the epidermis, but rarely in the dermis.
Vertical growth phase (VGP): called invasive MM; the tumor cells invade downward into the dermis and accumulate in the dermal papillae, usually with a cell count of 20-25 and a nuclear division pattern. In the late vertical growth phase or developmental phase, nuclear schizophrenia is common and tumor cells invade the reticular dermis and even subcutaneous fat. The nests of tumor cells in the epidermis are larger than in the radiogenic stage.