Melanoma, a cancer originating in pigment-producing melanocytes, is most commonly associated with the skin but can also develop internally. These internal forms are much rarer and harder to detect. This article explores their nature, rarity, detection challenges, and potential signs.
Understanding Internal Melanoma
Internal melanoma arises from melanocytes located in tissues other than the skin. Melanocytes exist beyond the epidermis in areas like the eyes, mucous membranes, brain, and spinal cord.
Uveal melanoma, which affects the eye, is the most common type of internal melanoma, originating in the iris, ciliary body, or choroid. Mucosal melanoma develops in the moist linings of the body, such as the nasal passages, mouth, esophagus, anal canal, or vagina. In rare instances, melanoma can also affect the central nervous system, known as leptomeningeal melanoma, which arises from melanocytes within the meninges, the membranes surrounding the brain and spinal cord.
The Rarity of Internal Melanoma
Cutaneous melanoma accounts for the vast majority of cases, with an estimated 100,000 new diagnoses annually in the United States. In contrast, internal melanomas collectively represent less than 5% of all melanoma diagnoses.
Uveal melanoma, the most frequent internal type, has an incidence of approximately 5 to 6 cases per million people per year in the United States. Mucosal melanoma is even rarer, accounting for about 1% of all melanoma cases. Leptomeningeal melanoma is exceedingly rare, with only a few hundred cases reported globally.
Why Internal Melanoma is Difficult to Detect
The hidden locations of internal melanomas present significant challenges for early detection. Unlike skin melanoma, which can often be visually identified through self-examinations or dermatological screenings, internal forms are not visible. This means initial growth can occur without outward signs or symptoms.
Symptoms of internal melanoma are often non-specific, mimicking those of many other conditions. This lack of distinct symptoms can lead to delayed diagnosis, as individuals may not recognize the need to seek medical attention. Routine health screenings typically do not include specific checks for internal melanomas, unlike skin cancer screenings. Consequently, internal melanomas are frequently diagnosed at a more advanced stage, after they have grown larger or spread.
Recognizing Potential Signs
While internal melanoma can be challenging to detect, certain signs and symptoms may indicate its presence and warrant medical evaluation. For uveal melanoma, changes in vision, such as blurry vision, flashes of light, or dark spots, can be indicators. Eye pain or a change in pupil shape may also occur. However, these symptoms can also be caused by many other common eye conditions.
Mucosal melanoma signs vary depending on the affected site but can include unexplained bleeding, a mass, or persistent pain in areas like the mouth, nasal passages, or genital region. For example, oral mucosal melanoma might present as a dark spot or lesion that does not heal. Leptomeningeal melanoma may cause neurological symptoms such as headaches, seizures, or changes in cognitive function. Any persistent or unusual health changes, especially those that worsen, should prompt a visit to a healthcare professional for assessment.