What Is Amelanotic Melanoma?

Malignant melanoma is a tumor produced by melanocytes from the skin and other organs. Skin melanoma is manifested as pigmented skin lesions that change significantly over months or years. Although its morbidity is low, its malignancy is high, metastasis occurs early, and mortality is high. Therefore, early diagnosis and early treatment are important. Malignant melanoma mostly occurs in adults, and cases of giant congenital pigmented nevus secondary to cancer are more common in children.

Basic Information

English name: malignant melanoma
Visiting department: Dermatology, Oncology

Multiple groups: Mostly occurs in adults
Common causes: May be related to genetic, environmental and other factors
Common symptoms: Local skin bleeding, itching, tenderness, ulcers, etc.

Causes of malignant melanoma

The etiology has not been fully elucidated. Some research data suggest that its occurrence is related to the following risk factors: genetic, environmental and genetic / environmental common factors. Such as atypical (dysplastic) mole or melanoma family history, light-induced pigmented skin, difficult to tanned skin, red hair race, strong intermittent sun exposure, sunburn, multiple melanocyte moles, etc. Multiple genetic / environmental factors lead to malignant transformation of melanoma. Key cell pathways of malignant transformation: Rb pathway, p53 pathway, PI3K / AKT pathway, RAS / MAPK pathway (20-30% NRAS mutation, 55-60% BRAF mutation).

Clinical manifestations of malignant melanoma

The clinical symptoms of skin malignant melanoma include bleeding, itching, tenderness, ulcers, etc. Generally speaking, the symptoms of melanoma are related to the age of onset. Young patients generally show itching, color changes and enlarged boundaries of skin lesions. Patients generally show ulcers on the skin lesions, which usually indicate a poor prognosis.

The skin lesions of skin malignant melanoma are related to the anatomical site and the growth mode of the tumor, that is, to the histological type, and the histological type varies greatly depending on age, type, and ethnicity. Different types of melanoma have different etiology and genetic background. Currently, clinical classification of melanoma uses Clark classification, including four types: malignant freckled nevus-like melanoma (LMM); superficial diffuse melanoma Tumor; freckled melanoma / mucosal melanoma; nodular melanoma (NM). About 70% of white people with malignant melanoma are SSM. But in all Asians with malignant melanoma, 72% of ALMs occur in areas with less sunlight.

Diagnosis of malignant melanoma

For suspicious skin lesions, ABCDE criteria can be used to judge. A (Asymmey) represents asymmetry, B (Borderirregularity) represents border irregularity, C (Colorvariegation) represents color diversity, D (Diameter> 6mm) represents diameter greater than 6mm, and E (Elevation, evolution) represents skin lesions bulge and progress. If the skin lesion meets the ABCDE criteria, malignant melanoma is highly suspected, and a biopsy for histopathological examination is required to confirm the diagnosis. However, the skin lesions of some subtypes such as nodular melanoma cannot be judged by the ABCDE standard.

Histopathology: abnormal proliferation of melanocytes, forming some cell nests in the epidermis or epidermal-dermal boundary. These cell nests vary in size and can fuse with each other. There are varying degrees of variation in the size and shape of melanocytes in the nest, as well as the shape of the nucleus. Mitosis (including abnormal mitosis) is more common than benign pigmented nevus, with pigment particles in the cytoplasm of tumor cells. In aggressive malignant melanoma, tumor cells infiltrate into the dermis or subcutaneous tissue. Immunohistochemical staining: tumor cells were S100 positive, HMB45 positive, and MelanA positive.

Pathological grade:

1. Invasion depth classification Clark (1969) studied melanoma invasion depth and prognosis, and classified melanoma into 5 levels according to the depth of invasion. The higher the grade, the worse the prognosis.

Grade I: Tumor cells are limited to the epidermis above the basement membrane.

Grade II: Tumor cells break through the basement membrane and invade the dermal papilla.

Grade III: Tumor cells filled the dermal papillary layer and invaded further, but did not reach the dermal reticular layer.

Grade IV: Tumor cells have invaded the reticular layer of the dermis.

Grade V: Tumor cells have penetrated the dermal reticular layer and invaded the subcutaneous fat layer.

2. Vertical thickness classification Breslow (1970) studied the relationship between vertical thickness and prognosis of melanoma. According to the thickest part of melanoma (thickness from the granular layer to the deepest part of melanoma) measured by eyepiece micrometer, melanoma was divided Level 5:

Less than 0.75 skin malignant melanoma, 0.76 to 1.50 skin malignant melanoma, 1.51 to 3.00 skin malignant melanoma, 3.01 to 4.50 skin malignant melanoma, and more than 4.50 skin malignant melanoma. It was found that the greater the thickness, the worse the prognosis. This micro-grading method has been widely used in the future and has proved to be of great value in judging prognosis.

Malignant melanoma treatment

Early non-metastatic lesions should be surgically removed, and the range of normal skin around the lesion should be determined according to the depth of Breslow. If it refers to (toe) malignant melanoma, truncated (toe) surgery can be used. Involved lymph nodes should be removed, but prophylactic lymphadenectomy is still controversial. Anti-mitotic drugs for limb arterial infusion have some effect in treating limb melanoma. For patients with extensive metastases, combined chemotherapy and radiation therapy can be used. Biochemical therapy and molecular targeted therapy have great prospects.

Prognosis of malignant melanoma

Depends on the stage at the time of diagnosis. Prognosis is better in patients with no local lymph nodes and distant metastases. The survival rate of stage / women is higher than that of men, and the primary melanoma of the trunk, head and neck is worse than that of the limbs. The advanced age is inversely proportional to the survival rate of melanoma. Stage III melanoma has significantly different prognosis: the number of ulcers and lymph node metastases indicates a poor prognosis. Stage IV melanoma is an important prognostic factor for distant metastasis. Skin and distal lymph nodes) have a poor prognosis.