Malignant Melanoma Clinical Types and ABCDE
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Direct answer
Malignant melanoma is a malignant tumour of melanocytes that presents in four classical clinical types: superficial spreading, nodular, lentigo maligna and acral lentiginous. Superficial spreading is the commonest type in fair-skinned people, while acral lentiginous melanoma dominates on palms, soles and nail beds in darker skin. The ABCDE rule (asymmetry, border, colour, diameter and evolution) is the standard bedside screen for suspicious pigmented lesions.
What you must remember
- Superficial spreading: commonest type in white skin, typically on the trunk in men and the legs in women, with a radial growth phase before vertical invasion.
- Nodular melanoma: grows vertically from the outset, is often amelanotic and thickens quickly, so it presents thick and carries a poor prognosis.
- Lentigo maligna melanoma: the invasive form of lentigo maligna, which appears as a Hutchinson freckle on sun-damaged face in older people; the in situ phase is long.
- Acral lentiginous melanoma: affects palms, soles and subungual sites; it is the dominant subtype in darker-skinned people and is often diagnosed late.
- ABCDE criteria: asymmetry, border irregularity, colour variegation, diameter over 6 mm and evolution in size, shape or colour.
- Ugly duckling sign: a lesion that looks different from the patient's other naevi is suspicious even when it meets few ABCDE criteria.
- Dermoscopy: atypical pigment network, blue-white veil, irregular dots and globules and regression structures support melanoma.
Subtypes compared by site and growth pattern
Each subtype is recognised by its site, growth phase and typical age group, which is what exam stems describe. The table sets the four classical types side by side.
| Subtype | Typical site | Growth pattern | Prognostic note |
|---|---|---|---|
| Superficial spreading | Trunk in men, legs in women | Radial, then vertical | Best outlook when thin |
| Nodular | Anywhere, including trunk and head | Vertical from onset | Thick at diagnosis, poor outlook |
| Lentigo maligna | Sun-damaged face of older people | Slow radial growth, long in situ phase | Good when excised early |
| Acral lentiginous | Palms, soles and nail bed | Radial, then vertical | Poor when late; common in darker skin |
Acral and mucosal types form a larger share of melanomas in Indian series than in most Western series, so palmoplantar and subungual lesions should not be dismissed. The ABCDE rule screens for lesions but does not diagnose them, and dermoscopy with biopsy confirms the subtype.
Where the subtype questions catch the unwary
Subtype questions usually turn on site and age, so read the stem for both before choosing an answer.
- Trap: assigning acral melanoma to sun-exposed skin because melanoma is commonly sun related. Correct: acral lentiginous melanoma sits on palms, soles and nail beds, not on sun-exposed skin.
- Trap: calling lentigo maligna benign because it grows slowly. Correct: it is an in situ melanoma that can invade, so it needs biopsy and excision.
- Trap: using the ABCDE rule to exclude melanoma when the criteria look absent. Correct: small, symmetrical or amelanotic nodular melanomas can escape ABCDE, so a firm, growing lesion still needs biopsy.
Frequently asked questions
Which melanoma subtype is most common in fair-skinned people?
Superficial spreading melanoma is the most common subtype in fair-skinned people and typically affects middle-aged adults. Its radial growth phase means that early excision often finds a thin lesion with a good prognosis.
What is the Hutchinson freckle?
Hutchinson freckle is an older name for lentigo maligna, a flat, irregularly pigmented macule on the sun-damaged face of older people. It is a melanoma in situ, and its invasive form is called lentigo maligna melanoma.
Which melanoma subtype is important in Indian patients?
Acral lentiginous melanoma is the dominant subtype in darker-skinned populations, and many Indian series report a large share of acral and mucosal melanomas. Its favoured sites are palms, soles and nails, so suspicious pigmentation there should be biopsied promptly.
Can nodular melanoma look non-pigmented?
Yes, nodular melanoma is often amelanotic or only lightly pigmented, so it can resemble a pink papule or nodule. A firm, elevated, growing lesion warrants biopsy even without strong colour change.
What does the ABCDE rule fail to detect?
The ABCDE rule does not reliably detect small, symmetrical, uniformly coloured or amelanotic melanomas, so it is a screening aid rather than a diagnosis. Dermoscopy and histopathology confirm the diagnosis, and any evolving lesion should be biopsied.