American Melanoma Institute · 4 min read
Some melanomas are raised, fast-growing, or pink instead of flat and dark. Learn the EFG rule and why a new, firm, growing bump needs a visit.
The ABCDE checklist (asymmetry, border, color, diameter, evolving) has taught millions of people to watch for a flat, dark, irregular mole that slowly changes. That picture fits the most common kind of melanoma, the superficial spreading type, which expands sideways across the skin for months or years before it grows downward.
Melanoma has 2 forms that don't match the picture. Nodular melanoma grows downward from the start. Amelanotic melanoma makes little or no pigment. A single tumor can be both, and these are the melanomas most likely to be overlooked by patients and doctors alike.
Nodular melanoma accounts for about 15% of melanomas in Australia and New Zealand, according to DermNet. The Melanoma Research Alliance notes that it causes a disproportionate number of melanoma deaths.
The reason is speed and direction. The outlook for any melanoma depends mostly on its thickness, measured in millimeters from the skin surface to the deepest tumor cell (the Breslow depth). A superficial spreading melanoma may spend a long time less than 1 mm thick. A nodular melanoma skips that flat phase. DermNet describes tumors that penetrate deep into the skin within a few months of first appearing, so many are already thick when diagnosed.
Nodular melanoma is somewhat more common in men and in people over 50. It can appear anywhere, including the head and neck, trunk, arms, and legs. It usually arises on skin that looked normal before, so watching existing moles will not catch it.
Picture a small dome. The typical nodular melanoma is a raised, round, symmetrical bump with a smooth surface and a regular edge. Often the bump is 1 color throughout: black, blue-black, brown, red, or pink. Measured against ABCDE, it can pass on asymmetry, border, and color.
People often describe it as a blood blister or pimple that never went away. As it enlarges, the surface may break down, crust, or bleed after minor contact such as toweling off.
Australian dermatologists added 3 letters to fill the gap:
A spot with all 3 features that persists for more than a month needs a prompt medical opinion, whatever its color. Growth is the most telling of the 3. Insect bites and pimples go away within a few weeks.
Melanoma cells come from melanocytes, the cells that make the pigment melanin. Most melanomas keep producing pigment, which gives them their brown or black color. Some lose that ability. The result is an amelanotic melanoma, which may be pink, red, skin-colored, or nearly clear. Many are hypomelanotic, meaning a faint tan or gray tint remains, often only at one edge.
DermNet estimates that amelanotic and hypomelanotic tumors make up about 2% to 20% of melanomas, a wide range that reflects how differently studies define the term. Any subtype can be amelanotic. About a third of nodular melanomas lack pigment, as do 25% to 50% of melanomas under the nail and more than half of desmoplastic melanomas, a rare scar-like type found on sun-damaged skin.
A flat amelanotic melanoma can look like a patch of eczema or an actinic keratosis that doesn't respond to treatment. A raised one can look like a basal cell carcinoma, a wart, a dermatofibroma, or a pyogenic granuloma (a benign, easily bleeding red bump). Under a dermatoscope, a lighted magnifier, the clues are in the blood vessels: a mix of dotted and irregular linear vessels, milky-red areas, and white lines.
Since appearance is unreliable, dermatologists lean on history. A pink or red spot that is new, persistent, and growing, or that returns after being frozen or treated with cream, often gets a biopsy even when it looks bland. A useful detail to bring to a visit is a timeline: when you first saw the spot and how it has changed. Dated phone photos with a coin or ruler for scale make that history concrete.
For a raised spot, doctors try to remove the whole thing, or at least sample its full depth, with an excisional, punch, or deep shave biopsy. A shallow shave that cuts through the middle of a nodular melanoma makes the thickness impossible to measure accurately, and thickness guides every later decision.
Once diagnosed, nodular and amelanotic melanomas are staged and treated like any other skin melanoma of the same thickness. Treatment begins with a wide excision, a surgery that removes the biopsy site with a margin of normal skin, and thicker tumors receive wider margins.
Because nodular melanomas are often thicker than 1 mm at diagnosis, a sentinel lymph node biopsy is frequently part of the discussion. In this procedure, the surgeon finds and removes the first lymph node that drains the tumor site, and a pathologist checks it for melanoma cells. Depending on the stage, doctors may then recommend immunotherapy after surgery to lower the risk of recurrence, and in some stage III cases before surgery as well.
The risk of spread rises with thickness, and a nodular melanoma can cross from one thickness category into the next within months.
