Amelanotic melanoma

Synonyms
amelanotisches malignes Melanom, hypomelanotisches Melanom, pigmentarmes Melanom, Hypomelanotic melanoma
Specialty
Dermatology · Skin tumours
Images
Clinical 1 · Histology 1
In the app
5 flashcards
Last updated
10/2026 · Dr. Pascal Bafteh
Contents
  1. Images (2)
  2. Definition
  3. Occurrence & epidemiology
  4. Clinical features
  5. Diagnosis
  6. Differential diagnoses
  7. Keep learning in the app
  8. References (selection)
  9. Cross-references

Images (2)

Amelanotic melanoma – clinical photo: Reddish, pigment-poor nodule – amelanotic malignant melanoma
Reddish, pigment-poor nodule – amelanotic malignant melanoma (photo: Dr. Thomas Brinkmeier, Wikimedia Commons, CC BY 4.0)Dr. Thomas Brinkmeier, „Amelanotisches, malignes Melanom, ©wikiderm.de", CC BY 4.0, via Wikimedia Commons · CC BY 4.0 · Source
Amelanotic melanoma – histology (H&E), detail (specimen from a melanoma metastasis): densely packed spindled and epithelioid tumour cells with marked nuclear pleomorphism and prominent nucleoli, entirely free …Histology
histology (H&E), detail (specimen from a melanoma metastasis): densely packed spindled and epithelioid tumour cells with marked nuclear pleomorphism and prominent nucleoli, entirely free …Yale Rosen, „Metastatic melanoma Case 171", CC BY-SA 2.0, via Wikimedia Commons · CC BY-SA 2.0 · Source
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Definition

In amelanotic melanoma the tumour cells produce little or no pigment. The term is often also used for melanomas that are only partly devoid of pigment (hypomelanotic); completely pigment-free melanomas are rare. Any melanoma subtype can be amelanotic.

Occurrence & epidemiology

Depending on the definition, about 2–20% of all melanomas are classed as amelanotic. Risk factors are older age, chronically sun-damaged skin, fair skin, red hair, marked freckling and a tendency to sunburn; amelanotic melanoma also accounts for a considerable proportion of melanoma in children. About 25% of subungual melanomas and over 50% of desmoplastic melanomas are amelanotic.

Clinical features

  • Skin-coloured, pink or red macules, plaques or nodules, sometimes scaly; at the edge there may be faint light tan or grey pigmentation; borders well or ill defined.
  • Nodular forms resemble a skin-coloured naevus or basal cell carcinoma; other mimics include pyogenic granuloma and keratoacanthoma.
  • The ABCDE criteria are often not met; asking about red, raised, recent change helps.
  • Melanoma metastases may be amelanotic even when the primary tumour was pigmented.

Diagnosis

  • History of a new or changing lesion and examination of the entire skin.
  • Dermoscopy: the vascular pattern is decisive – polymorphous vessels, most frequently a combination of dotted and linear irregular vessels, milky-red areas; possibly remnants of irregular pigmentation.
  • Histology confirms the diagnosis. The absence of melanin granules (e.g. on Fontana-Masson staining) makes classification harder; immunohistochemistry demonstrates the melanocytic origin. The report includes Breslow thickness, ulceration and mitotic rate, among other features.

Differential diagnoses

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References (selection)

  1. DermNet: Amelanotic melanoma
  2. MSD Manual Professional: Melanoma (Abschnitt Amelanotic melanoma)

Cross-references

Mentioned in

More skin tumours

Note: This page is intended for medical education and does not replace diagnosis or treatment decisions in individual cases.