Fact-sheet: Malignant melanoma
Updated on 09/27/2024 at 9:02 AM
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Definition
Malignant tumor arising from melanocytes
Clinical features
ABCDE rule:
- Asymmetry
- Irregular borders
- Color heterogeneity
- Diameter (>6mm)
- Evolution (rapid recent change).
Pruritus or bleeding on contact.
Laboratory findings
Nonspecific
Radiography
No indication
Ultrasound
Highly valuable +++ in diagnosing nodal metastases in stage II or III!
- enlarged, spherical, markedly hypoechoic node (or even anechoic with posterior enhancement)
- loss of the hyperechoic hilum
- Doppler: disappearance of hilar vessels.
More subtle signs (Se +++ but low Sp):
- hypoechoic nodule within an otherwise normal node
- eccentric hilum
- asymmetric cortical thickening.
If node involved: surgical biopsy before lymph node dissection.
If uncertain: fine-needle aspiration
CT
Metastases often hypervascular: value of an arterial phase ++.
Pitfall: ubiquitous location of metastases requiring careful analysis!
MRI
T1: variable signal, dependent on melanin concentration
T2: hyperintense signal
After injection: intense enhancement.
Importance of detecting brain metastases: induces a change in chemotherapy +/- stereotactic radiotherapy
Pitfall: ubiquitous location of metastases requiring careful analysis!
Vascular intervention
Biopsy for pathological confirmation of metastases
Nuclear medicine
Staging workup.
Hypermetabolism on PET scan (18 FDG)
Management
Breslow < 0.8mm without ulceration: no imaging required
Breslow ≥ 0.8mm and/or ulceration:
- Ultrasound of soft tissues around the lesion looking for subcutaneous in-transit metastases
- Ultrasound of lymph node stations two echelons downstream of the melanoma - all cervical areas for the head If pathological lymph node: ultrasound-guided core biopsy
Staging workup based on multidisciplinary tumor board decision: brain MRI, chest-abdomen-pelvis CT or 18 FDG PET-CT.
Classification
Stage 0 In situ tumor Stage IA: Tumor ≤ 1 mm thick, without ulceration and mitoses < 1/mm2 (pT1a), N0, M0 Stage IB: Tumor ≤ 1 mm thick, with ulceration and/or mitoses ≥ 1/mm2 (pT1b), N0, M0 Tumor > 1 mm and ≤ 2 mm thick, without ulceration (pT2a), N0, M0 Stage IIA: Tumor > 1 mm and ≤ 2 mm thick, with ulceration (pT2b), N0, M0 Tumor > 2 mm and ≤ 4 mm thick, without ulceration (pT3a), N0, M0 Stage IIB: Tumor > 2 mm and ≤ 4 mm thick, with ulceration (pT3b), N0, M0 Tumor > 4 mm thick, without ulceration (pT4a), N0, M0 Stage IIC: Tumor > 4 mm thick, with ulceration (pT4b), N0, M0 Stage IIIA: Tumor without ulceration (pT1a-4a), microscopic metastases in 1, 2 or 3 regional lymph nodes (N1a, 2a), M0 Stage IIIB: Tumor without ulceration (pT1a-4a), macroscopic metastases in 1, 2 or 3 regional lymph nodes or in-transit metastases (N1b, 2b, 2c), M0 Tumor with ulceration (pT1b-4b), microscopic metastases in 1, 2 or 3 regional lymph nodes or in-transit metastases (N1a, 2a, 2c), M0 Stage IIIC: Tumor with ulceration (pT1b-4b), macroscopic metastases in 1, 2 or 3 regional lymph nodes (N1b, 2b), M0 Tumors with or without ulceration (any pT), metastases in 4 or more regional lymph nodes or in-transit metastases with regional lymph node metastasis(es) (N3), M0 Stage IV: Distant metastases (any pT, any N, M1)
Differential diagnosis
Common melanocytic tumors: nevi
Seborrheic keratoses
"Pigmented" basal cell carcinomas
Pigmented dermatofibromas
Thrombosed angiomas