Primary intracranial malignant melanoma

Primary intracranial malignant melanoma is an exceptionally rare type of cancer that originates in the brain and is composed of melanocytes, the pigment-producing cells usually found in the skin. Melanocytes are responsible for the production of melanin, the pigment that gives color to the skin, hair, and eyes. When these cells become malignant and form a tumor within the brain, it is referred to as primary intracranial malignant melanoma.

Key points about primary intracranial malignant melanoma include:

Rare Incidence: Primary intracranial malignant melanoma is extremely rare, accounting for only a small percentage of all brain tumors. Melanoma more commonly originates in the skin and, less frequently, in the eyes (ocular melanoma).

Origin: Unlike most brain tumors that arise from brain cells, primary intracranial malignant melanoma originates from melanocytes that have migrated into the brain during embryonic development or are otherwise present in the meninges (the layers of tissue covering the brain).

Diagnostic Challenges: Diagnosing primary intracranial malignant melanoma can be challenging. It may be initially mistaken for other types of brain tumors or metastatic melanoma from other parts of the body.

Aggressive Nature: Malignant melanomas are known for their aggressive behavior, and primary intracranial melanomas are no exception. They tend to grow rapidly and may infiltrate nearby tissues.

Symptoms: The symptoms of primary intracranial malignant melanoma are similar to those of other brain tumors and may include headaches, seizures, neurological deficits, and changes in behavior or cognitive function.

Treatment: Treatment typically involves a combination of surgery, radiation therapy, and, in some cases, chemotherapy. Due to the rarity of this condition, there may not be well-established treatment guidelines, and the approach may be tailored based on the individual patient's condition.

Prognosis: The prognosis for primary intracranial malignant melanoma is generally poor due to its aggressive nature and the challenges associated with treatment. The outcome can vary depending on factors such as the tumor size, location, and the extent of surgical resection.

It's important to note that primary intracranial malignant melanoma is distinct from metastatic melanoma, where melanoma spreads to the brain from another primary site, often the skin. Overall, the rarity of this condition makes it a challenging area for research and clinical management.

A case of a man with a history of rapidly arising motor slowing associated with urinary incontinence, presenting with mild convergent strabismus caused by paralysis in abduction in the right eye. A brain CT showed a lesion compatible with malignant sphenoorbital meningioma, and the patient underwent gross total resection. Intraoperatively, the blackish lesion infiltrated and eroded the bone; it was placed externally on the dura mater with a mild reaction and without attachment. Histological examination confirmed PIMM.Intraosseous localisation of PIMM has been observed in the basic bone structure of the oral cavity. They report the first intraosseous spheno-orbital PIMM case and present an embryological theory about how this unusual tumour can develop 1).

Guarrera B, Coati I, Giarletta M. Unusual case of intraosseous primary intracranial malignant melanoma. BMJ Case Rep. 2024 Jan 25;17(1):e256623. doi: 10.1136/bcr-2023-256623. PMID: 38272513.
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