- Clinical science
Melanoma, a highly malignant tumor arising from melanocytes, is the most common life-threatening dermatological disease. Risk factors include UV radiation exposure, particularly in light-skinned individuals that are easily sunburned, increasing age, family history, and immunosuppression. The superficial spreading melanoma is the most common subtype. Other subtypes, such as nodular melanoma, have a significantly worse prognosis because they tend to metastasize more rapidly. Invasive melanoma is particular in its propensity to metastasize to unusual locations that are not commonly affected by other malignancies. Immediate full-thickness surgical excision of the primary tumor is usually the best initial diagnostic test and may be therapeutic for localized disease. Chemotherapy, biologics, and/or radiation therapy is recommended for recurrent or widespread disease. Tumor thickness is the most important prognostic factor.
Most common life-threatening dermatological disease
Epidemiological data refers to the US, unless otherwise specified.
- Risk factors
- Pruritic, persistently bleeding skin lesion
Dermoscopy should be used to examine lesions for ABCDE criteria:
- A = Asymmetry
- B = Border (irregular border with indistinct margins)
- C = Color (new changes in pigmentation or variations in pigmentation within the same lesion)
- D = Diameter > 6 mm
- E = Evolving (new lesion or a lesion that changes in size, shape, or color over time)
|Frequency and characteristic features||Predilection sites||Clinical appearance||Growth|
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- Epidemiology: more common in African-American and Asian populations
- Mucous membranes
- Palms and soles
- Prognosis: Generally good because of relatively slow horizontal growth pattern. Late diagnosis often occurs, however, due to poorly visible predilection sites (e.g., sole of the foot)
- Pink or skin-colored nodes → may be difficult to recognize
- Histological diagnosis is necessary
- Metastatic melanoma may spread to lymph nodes, liver, lung, brain, and bone
- May also metastasize to strange locations not typically affected by other metastatic malignancies (e.g., cardiac metastases, gallbladder)
- Up to 5% of metastatic cases have no known primary lesion.
- Characteristic black pigmentation
A full-thickness excisional biopsy (best diagnostic test) is indicated in all suspicious lesions.
- An excisional biopsy procedure used to obtain a tissue sample of skin that includes every layer (i.e., healthy and abnormal tissue)
- Pathology shows positive, epithelioid cells with fine granules in cytoplasm
- Staging tests (e.g., ultrasound or MRI) once diagnosis confirmed: to determine tumor thickness, spread to lymph nodes, or distant metastasis
Complete excisional biopsies are always preferred over incisional biopsies, as they allow tumor thickness to be properly estimated!
|Differential diagnosis of common skin cancers|
|Color||Morphology||Location||Other characteristic features|
|Melanoma|| || || || |
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Benign lesions commonly resemble melanomas and should be biopsied to rule out cancer (see )!
The differential diagnoses listed here are not exhaustive.
Full-thickness incision with appropriate safety margins
0.5 cm safety margin
- Suspicious lesion without proven melanoma →
- Melanoma in situ (T0) → 0.5 cm safety margin
- Other margins: according to Breslow's depth: thickness from the granular layer to the lowest detectable tumor cell
|Breslow stage||Modified by AJCC (valid since 2001)||Safety margin|
|I||≤ 1.0 mm||1 cm|
|II||1.01–2 mm||1–2 cm|
|III||2.01–4 mm||2 cm|
|IV||≥ 4 mm|
|If tumor thickness > 1 mm (Breslow stage ≥ II): perform sentinel lymph node biopsy|
The gold standard is immediate, complete excision of the tumor!
- Survival rate is highly unpredictable
|TNM classification and Breslow thickness||Estimated 5-year survival rate|
|T1 (< 1mm), no nodular involvement, no metastases |
|Up to T4 (> 4 mm), no nodular involvement, no metastases||≈ 70 %|
|N1, regional skin metastases |
(no distant metastases)
|≈ 20–40 %|
|M1, distant metastases||< 5 %|
Negative prognostic factors
- Epidemiological features: male sex
- Clinical features: type , localization , and presence of ulcerations
- Tumor thickness is the most important prognostic factor.