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Diagnostics of malignant melanoma

The dramatic increase in the number of malignant melanoma in the skin has lead to an increased awareness in the population of the association between sunbathing and malignant melanoma. People with moles seek medical advice earlier than in previous years.

A thorough anamnesis should always be performed, as well as adequate examination and dermatoscopy. For examination of suspect skin lesions, a systematic approach is beneficial.

Malignant melanoma which is asymmetric, has an uneven border, and irregular color. Click to enlarge.

ABCD rule is a helpful tool:
  • A – Asymmetry
  • B – Border. These lesions usually have an irregular, notched, ragged, or blurred edge.
  • C – Color. The color is irregular and often with black parts.
  • D – Diameter. Moles that are usually 6 mm in diameter or larger.
  • E – Elevation

The final diagnosis is based on histopathological examinations of the lesion. In cases where the tumor is localized to the face in elderly, fragile individuals, or for suspicion of malignancy in a small part of a large lesion, it may be appropriate to take a biopsy for a histological diagnosis.

Tangential biopsies are contraindicated because specification of the Breslow tumor thickness is then not possible. Excisional biopsy of pigmented lesions, where malignant melanoma cannot be ruled-out, can be carried out by a dermatologist or general practitioner. For large lesions or in cosmetically sensitive locations such as the face, the excision should be carried out by a surgeon/plastic surgeon.

Sentinel node (sentinel lymph node) is a diagnostic and prognostic procedure. It is not proven to improve survival and is not used routinely in Norway. Norwegian Melanoma Group proposes to implement sentinel node procedure for cutaneous melanoma localized to lower extremities, initially stage 2a. To reduce the number of sentinel node procedures, it is proposed that this starts at university hospitals and that the patients initially are screened with cytology samples and by a radiologist with extensive experience in ultrasound.

The National Institute of Health separates birth marks according to size:

  • small nevus < 1.5 cm
  • medium nevus 1.5–20 cm
  • large nevus > 20 cm

Moles can be described as atypical based on clinical and/or histological criteria. A clinically atypical mole:

  • is at least 5 mm large
  • is asymmetrical
  • has irregular borders and color variation

An excision should be done of an atypical mole if there is suspicion of malignancy. The patient should be referred to a dermatologist if he/she has an atypical mole or a family member with malignant melanoma for information, instruction, and follow-up.

For suspicion of malignant melanoma in a mucous membrane in the head/neck region, a clinical examination should be supplied with:

  • CT/MRI skull base/jugulum
  • CT thorax
  • ultrasound of liver 
  • blood status

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