A dark spot on your thumb nail is often a harmless bruise (subungual hematoma) from injury, appearing as a black, purple, or reddish smudge that grows out, but it could also signal a fungal infection (thick, crumbly), reaction to substances like dark nail polish, or, rarely, skin cancer (melanoma), which presents as a dark streak or mole. If you didn't have an injury, notice irregular streaks, widening spots, or changes in nail texture, see a doctor to rule out serious causes like melanoma or fungus.
Melanonychia is a brown or black discoloration on your nail. These can be harmless. But they may be a sign of an underlying condition or skin cancer. That's why it's important to get an accurate diagnosis. If you notice changes to your nails, contact a healthcare provider.
Like other types of melanoma, subungual melanoma develops in melanocytes, the pigment cells that give skin its color. Unlike most types of skin cancer, subungual melanoma isn't related to sun exposure. Nail melanoma often shows up as a narrow brown or black streak or band on the nail.
A black line on the nail describes a narrow, longitudinal stripe that forms under the nail plate. It often results from splinter hemorrhages, longitudinal melanonychia, and, in some cases, subungual melanoma. Doctors often diagnose the cause of nail marks by examining the nails and reviewing your medical history.
Because this streak often resembles a bruise, it's important to monitor how its appearance changes over time, especially if there was no known injury to the nail—a bruise will generally heal and move outward as the nail grows, while a streak caused by subungual melanoma will not heal or change positions (although it ...
Since the preliminary presentation of nail bed melanoma is brownish-black streak on the nail, it may often be misdiagnosed as benign conditions like onychomycosis, bacterial infection, subungual hematoma, pyogenic granuloma, subungual verruca, subungual exostosis, subungual hemorrhage, junctional nevi, glomus tumor, ...
Infected nails may turn yellow, brown, or even black as the fungus spreads and damages the nail structure. If left untreated, this condition can lead to brittleness, thickening, and sometimes a foul odor. Effective treatment often includes antifungal medications or, in stubborn cases, laser therapy.
Monitoring Changes in Nails
Be especially cautious with changes on your thumb, big toe, or cuticle areas, as subungual melanoma most often starts there. Regular self-examinations can help in early detection, making it crucial to monitor any unusual changes in these areas.
However, it can develop in any nails of the fingers and toes. Nail unit melanoma tends to be diagnosed equally among the sexes, and is most common in people between the ages of 50-70. However, anyone can develop this disease at any age.
The 5 key signs of melanoma, often remembered by the ABCDE rule, are Asymmetry (uneven halves), Border irregularity (ragged edges), uneven Color, a Diameter larger than a pencil eraser (6mm), and Evolving (changing) size, shape, or color, plus other signs like non-healing sores, itching, or bleeding from a spot.
“If the pigment band becomes wider than 3 millimeters (mm), especially near the cuticle; becomes more irregular in pigmentation, such as a mixture of light and dark brown shades; or develops blurred borders extending to the skin around the nail fold [or, bottom of the nail], you have historical indicators of nail ...
While there are some harmless causes of nails changing color, some are a warning sign of diseases, infections, anemia, and even poisoning. Watch out for unexplained changes to blue, white/pale, greenish-black, yellow, or red, which can affect either the whole nail or just parts of it. A dark streak.
Liver failure nails often appear as Terry's Nails, characterized by an opaque white or "ground glass" look across most of the nail, with only a thin, brownish or pinkish band at the very tip and the half-moon (lunula) often disappearing, though other changes like ridges or yellowness (jaundice) can also occur, indicating systemic issues.
Nail fungus is caused by various fungal organisms (fungi). The most common is a type called dermatophyte. Yeast, bacteria and molds also can cause nail infections. The discoloration from a bacterial infection tends to be green or black.
The survival rate is high when subungual melanoma is detected early. Survival rates are about 95% when it's caught at an early stage and treated quickly. If subungual melanoma is diagnosed later and cancer has spread, the survival rate can be as low as 15%.
Melanonychia is a brown or black stain in your fingernail or toenail. You can have a dark line on one nail, a few nails, or all of your nails. The line is caused by the natural color in your body called "melanin." It's the substance that colors your skin and hair.
When checking your nails for melanoma, dermatologists recommend looking for the following changes: A dark streak. This may look like a brown or black band in the nail — often on the thumb or big toe of your dominant hand or foot. However, this dark streak can show up on any nail.
A common cause of black spots on nails is trauma, such as a hit, pressure, or crushing injury. Blood collects under the nail, forming a dark-colored spot (subungual hematoma). This discoloration typically grows out with the nail over time.
Trauma or Injury: If something heavy falls on your nail, it can cause bleeding under the nail, resulting in a black spot or streak. Fungal Infection: Nail fungal infections can also lead to discolouration and black dots on nails. Melanoma: In rare cases, black spots on nails can indicate melanoma.
On the other hand, those white spots may indicate some deficiencies like zinc, calcium, or protein, though this is less common. Rarely, they can be linked to underlying health problems such as fungal infections or, more rarely, systemic conditions.
Acral lentiginous melanoma, the most common form of skin cancer on nails, looks like a dark band that runs from the nail matrix (where the nail begins to grow) outward toward the edge of your nail. Nodular melanoma takes the form of a bump that may originate beneath the nail.
Seborrheic keratosis doesn't turn into melanoma, but the two can be mistaken for each other. Both can be brown or black and appear anywhere on the body. There are some important differences, however: Seborrheic keratoses often appear in numbers, while melanoma is usually single.
With appropriate treatment, Stage I melanoma is highly curable. There is low risk for recurrence or metastasis. The 5-year survival rate as of 2018 for local melanoma, including Stage I, is 98.4%.
Equipment used for Nail Biopsy
For numbing your skin during the biopsy, a local anesthetic called 1% lidocaine solution is often used. This prevents you from feeling pain during the procedure.