What is Malignant Melanoma?

Melanoma is a pigmented nevus with malignant changes. It develops from junctional or mixed moles. Although it is not necessarily a malignant change in the nevus, chronic irritation and inappropriate treatment have a great relationship to the conversion of the nevus to melanoma. The heel is the most common site, followed by the head, neck, and limbs. Most cases have metastasized to regional lymph nodes, and can also metastasize to the bloodstream. The clinical diagnosis was based on pigment changes and clinical symptoms, and biopsy of the entire specimen. The best treatment is surgical resection. ^[1] In November 2019, Indian researchers used machine learning models to identify markers of 17 key genes related to skin melanoma, and the accuracy rate of distinguishing primary or metastatic melanoma was 89%. ^[2]

Melanoma

Melanoma refers to a malignant change

Melanoma is a malignant tumor that originates in cells that make melanin. It is characterized by the sudden appearance or rapid growth of moles, the deepening of the color, the appearance of comet-shaped nodules or pigment rings around it, localized pain, infection, ulcers or bleeding, and enlarged lymph nodes. Tumors occur in the lower limbs, followed by the head, neck, upper limbs, eyes, under nails, and labia. It can metastasize to the liver, brain, bone, and mucous membrane from the lymphatic tract and blood in the early stage. The incidence is closely related to the mole. Moles that often rub on the palms, soles of the feet, and eyes, as well as those at the junction of the epidermis and dermis, are prone to malignancy and are considered to be the precursor stage of melanoma.

Melanoma is also called malignant melanoma. It is a skin tumor related to orthopedics. Benign melanoma, also known as pigmented nevus, is mostly unnoticed. Melanoma can be malignant in the first place, but usually results from malignant nevus. This is a more malignant tumor and is more common. More common in adults over 30 years old, the male to female ratio is 2: 1. The most common sites are the lower limbs, with the feet as the most common, followed by the upper limbs, head and neck, and trunk. The cause is unknown, but some cases have a history of skin injuries. Burns and X-rays may be the cause. A few cases are related to endocrine factors. Familial tendencies have also been reported. The tumor was gray-black, nodular, soft, and sometimes ulcerated. Under the microscope, tumor cells are mostly spindle-shaped, round or polygonal. The cytoplasm contains unequal melanin particles, which are black in appearance, and the tumor cells are of different sizes, which are diffuse, nested, adenoid or trabecular. . This tumor should be treated promptly regardless of whether it is metastatic or not ^[3]

Most melanomas are primary and affect adults and children, especially those with neurocutaneous symptoms. Meningeal solitary melanoma occurs in the same location as benign melanoma, mostly in the posterior cranial fossa meninges and cervical meninges. Clinically, the patient presents with intracranial hypertension or neurological symptoms due to compression of the spinal cord by the mass.

Tumors are single solid, often with an envelope, and can be black, reddish-brown in color, varying in shade, or non-pigmented.

Histologically, the tumor arrangement is similar to melanoma, which is arranged in patches or bundles, and can also be nested. Tumor cells are pleomorphic, with obvious atypia. Large and weird tumor cells, including multinucleated giant cells, are found with varying amounts of melanin. The nucleoli is clear and mitosis is easy to see. Each high-power field has 6 to 10 fields. The brain and spinal cord infiltration are common. Some cases saw local necrosis and bleeding. Because some cases have no melanin deposits, according to the tumorigenesis site and the above morphology, the possibility of melanoma should be considered and not missed. If the malignant meningeal melanoma is accompanied by secondary diffuse meningeal spread or multiple lesions, it is called meningeal melanoma.

All non-pigmented meningeal tumors are included in the differential diagnosis, because these tumors are likely to be melanoma, especially those with a lamellar arrangement, consistent nuclear morphology, and obvious nucleoli. Once confirmed by immunohistochemistry and electron microscopy, it is necessary to identify whether it is primary or metastatic. However, most melanomas that metastasize to the brain are in the brain parenchyma, not the meninges. But to determine the metastatic tumor, it is necessary to combine clinical history and imaging examination.

The distinction between melanoma and benign melanoma is easier based on histomorphology, but the difficulty is the middle-level melanoma. Although not all cases can be clearly identified, it is important to emphasize the atypical nature of melanoma cells and the high number of mitotic cells, as well as the malignant characteristics of local necrosis. Nesting, epithelioid cytology, low Ki67 index, IV collagen and laminin deposition around the leaflets are all helpful for the diagnosis of melanoma.

In November 2019, a research team in India used a machine learning model to identify the markers of 17 key genes related to skin melanoma, and the accuracy rate of distinguishing primary or metastatic melanoma was 89%. A related paper was recently published in UK Scientific Reports website. ^[2]

Meningeal melanoma is a highly invasive tumor, so it tends to recur locally or spread to other organs through the cerebrospinal fluid. As with other isolated intracranial and spinal canal malignancies, surgical resection of primary melanoma and postoperative radiotherapy are the preferred treatments, but tumors are often resistant to radiation.

Tumor cells S-100 and melanocytes were positive for HMB-45 and melanA. GFAP, NFP, CK, and EMA were all negative, Ki67 labeling was 2% to 15%.

In August 2018, it was learned from the Peking University Cancer Hospital and the Chinese Cancer Society's Clinical Oncology Collaborative Professional Committee that the melanoma expert committee has increased the detection rate of melanoma in China, with about 20,000 new cases each year. ^[4]

On September 19, 2018, the "Key to Life-Cancer Immunotherapy Patients Assistance Project", which aims to provide medical assistance to patients with advanced melanoma in China's dibao and low-income families, was officially launched. After the project was launched, it was launched in more than 70 cities across the country. ^[5]