Atypical melanoma – what’s new in diagnosis and management?

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Melanoma in Australia?

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Melanoma awareness and early detection

Overall awareness of melanoma has improved. Superficial spreading melanomas in Australia are now detected earlier when tumours are thinner, resulting in a reduction in deaths from this subtype.[4,8]

However, we are less effective in detecting melanoma subtypes that have an atypical clinical appearance, such as nodular melanoma, desmoplastic melanoma and acral lentiginous melanoma. These subtypes are much less common than superficial spreading melanoma,[4,9] yet they account for a higher proportion of deaths (Table 1).[9]


Table 1. Relative incidence and mortality rate for invasive melanoma subtypes

Subtype

Typical population/site

Proportion of cases

Deaths

Superficial spreading melanoma

Younger people with naevi and history of intermittent sun exposure

57%

29%

Nodular melanoma

On head and neck of older people with chronically sun-damaged skin

14%

44%

Lentigo maligna

On head and neck of adult with chronically sun-damaged skin, with involvement of hair follicles, sweat ducts

8%

5%

Acral lentiginous melanoma

Older people of any skin type*

0.7%

3%

Desmoplastic melanoma

On head (including ears, lips, nose) and neck of older people with chronically sun-damaged skin

0.7%

2%

Source: Victorian Cancer Registry data [9]
*Acral lentiginous melanoma can occur in people with any skin type, including deeply pigmented skin. It should be considered even in groups usually assessed to be at low risk of melanoma, including Aboriginal and Torres Strait Islander people and those with Fitzpatrick skin phototype IV (people with moderate-brown skin who always tan well and burn minimally) to phototype VI (people with deeply pigmented skin), including immigrants.

GP skin checks

The majority of melanoma diagnoses occur in general practice.[3]

All GPs should be competent in performing skin checks, which involve a focused history and thorough examination of the patient’s whole skin surface, including scalp and feet. The optimal frequency of skin checks depends on the individual’s estimated risk level (Table 2).

Risk level is determined by a number of factors including:

  • age
  • gender
  • hair colour
  • history of melanoma
  • prevalence of:
    • moles
    • common and atypical naevi
    • freckles.

You can assess a patient’s risk with them during a consultation by using a risk calculator tool.

National guidelines recommend that clinicians who are performing skin examinations for the purpose of detecting skin cancer should be trained in and use dermoscopy.[4]

Patients should be advised that if a new lesion appears or an existing lesion changes after their skin check, they should attend for re-examination.[10]

Atypical melanoma remains challenging

Compared with superficial spreading melanoma, subtypes with atypical presentations are often diagnosed when they are much thicker lesions.[8] Improved diagnostic accuracy of these subtypes could enable early diagnosis and significantly reduce deaths from melanoma.

Tumour thickness is not necessarily due to diagnostic delay; while the common superficial spreading melanomas tend to grow slowly over several years, some nodular melanomas and desmoplastic melanomas will become thick and life-threatening over weeks to months.[4,8] These subtypes are more common on chronically sun-damaged skin, typically the head and neck, and predominantly occur in older men.[4]

Even the subtypes that usually show typical features (superficial spreading melanoma and lentigo maligna) can occasionally appear skin-coloured, making them much more difficult to recognise (Figures 1–2).

Recently updated national guidelines on the management of melanoma.[4] include a new chapter on recognising atypical melanoma. The new guidelines emphasise that awareness of ‘atypical’ features of melanoma is critical because there is narrow window of opportunity for both patients and doctors to detect rapidly growing lesions while they are still thin.[4,15]


National guidelines for managing atypical melanoma[4] – key messages for GPs

Any lesion that continues to grow or change in size, shape, colour or elevation over a period of more than one month should be biopsied and assessed histologically or referred for expert opinion.

Suspicious raised lesions should not be just monitored – they should be biopsied.

The best biopsy approach for a suspicious pigmented lesion is complete excision with a 2 mm clinical margin.

Figure 1. Typical superficial spreading melanoma

Figure 2. Superficial spreading melanoma with atypical features

Images reproduced with permission of Victorian Melanoma Service.

Recognising atypical melanomas

Melanomas that are already thick and life-threatening may lack the classical features of melanoma: asymmetry, border irregularity, colour variegation, and diameter > 6 mm (summarised as ABCD).[8] They can be symmetrical, dome shaped, or skin-coloured,[8] and may occur in unusual sites such as palms, soles or nail beds (Figures 3–5).

The ABCD criteria have been extended to include EFG (elevated, firm and growing) criteria (Table 3).[8]

For any suspicious lesion, ask how long it has been present and whether it has changed in shape, appearance or growth over time. Any lesion that is elevated, firm and growing over a period of more than a month should raise suspicion of melanoma.[8]

Melanoma should also be suspected for lesions that recur at the site of a previous biopsy diagnosed as benign on histopathology (eg, as dermatofibroma, neurofibroma, scar), or when a ‘wart’ does not respond to treatment or does not show the typical pinpoint vessels of a wart when pared down (4,8). Wart-like (verrucous) melanomas typically occur on the back, arms, legs of men older than 50 years.[5]

Up to 20% of all melanomas are only partially pigmented (hypomelanotic).[8] Completely amelanotic melanomas are much less common.[8] Hypomelanotic melanomas can mimic a range of other skin lesions (Table 4).[5,8]

Dermoscopy allows the visualisation of diagnostic features of pigmented skin lesions that are not seen with the naked eye, and can also identify diagnostic features in non-pigmented (amelanotic) lesions.[4]

Table 5 summarises morphology, macroscopic features and dermoscopic features of melanoma subtypes.[4,5]

Reassure, excise, refer or monitor?

Key message: Suspicious raised lesions should be excised and not monitored.

Short-term dermoscopic monitoring over 3 months is appropriate to review flat lesions that lack dermoscopic criteria for melanoma, but where there is any suspicion (or borderline suspicion) of melanoma, lesion should be excised.[4]

Any lesion that continues to grow or change (in size, shape, colour or elevation) for more than one month should be excised and sent for histopathology, or referred for urgent specialist assessment – do not monitor over time.[4]

Full excision biopsy with a 2 mm margin should be performed within 2 weeks.[3,4]

What to include on the pathology request

The histopathology request should provide as much relevant clinical information as possible (see Clinical information that may aid pathologists in the diagnosis of melanoma of the skin).[4]

Clinical details such as history of the lesion (including treatments) and history of other malignancy, and a diagram or photograph showing specimen orientation, can help the pathologist make a diagnosis of melanoma.[4]

Interpreting the histopathology

When a pathologist examines a histological slide of a skin lesion there are three possible diagnoses: clearly malignant, clearly benign and too close to call.[5]

If it is clearly benign or clearly malignant, the report is generally succinct. If the lesion is too close to call, the report may be long and raise uncertainty (Table 7). Call the pathologist to discuss the report. They may recommend review by a specialist dermatopathologist.[5]

Any unexpected pathology results should be discussed with the reporting pathologist.

Table 7. Clinical situations when the pathology report may be uncertain


Issue


Action

Partial biopsies

Partial biopsy can make it difficult for the pathologist to make an accurate histological assessment. The report may be uncertain or discordant with the clinical picture.

If there is any uncertainty, excise the lesion completely or refer the patient for excision.

Spitzoid lesions

Spitzoid lesions can be particularly difficult to diagnose on histopathology

The pathologist may recommend review by a specialist dermatopathologist.

Recurrence of ‘benign’ lesion

Recurrence at the site of a previous biopsy diagnosed as benign on histopathology (eg, as benign naevus, dermatofibroma, neurofibroma, scar) should raise suspicion of melanoma.[8]

Excise the lesion completely or refer the patient for excision.

More information: follow-up after a diagnosis of melanoma

Re-excision

If the histopathological diagnosis of melanoma is confirmed after initial excision biopsy, re-excision is required to achieve definitive complete histological clearance according to recommended margins.[4,11]

Most thin primary melanomas can be treated as an outpatient under local anaesthesia or as a day-case.[4]

After excision margins have been assessed histologically, some patients may need re-excision (eg if initial margins are unacceptable).

Sentinel lymph node biopsy is indicated if melanoma greater than 1 mm thickness is detected (or greater than 0.75 mm when other high-risk pathological features are present). If sentinel lymph node biopsy is indicated, the surgeon should perform this at same time as wide excision.[4] Complete lymph node dissection is no longer recommended for most patients with positive sentinel node biopsy. Active surveillance achieves equivalent 3-year melanoma-specific survival with less morbidity.[4] Patients with a positive sentinel node should be referred to a medical oncologist to discuss adjuvant therapies.

Follow-up care plan

If the diagnosis or follow-up occurs in a specialist setting, the lead clinician should provide you with the patient’s treatment summary and follow-up care plan, and should discuss these with you.[3]

Refer to current guidelines for guidance on follow-up after definitive treatment of melanoma, including follow-up intervals.[4]

Staging and prognosis

For patients with a diagnosis of primary cutaneous melanoma that has not spread beyond primary site (asymptomatic stage I and stage II), staging is based on the histopathology. Imaging studies are not required for initial staging.[4]

Melanoma prognosis is based on American Joint Committee on Cancer (AJCC) stage.[7] An individual’s prognosis can be estimated using the AJCC’s Individualized Melanoma Patient Outcome Prediction Tools available online.

Melanoma survivors should be made aware of their risk of developing more primary melanomas and their need for lifelong skin surveillance. Advise on protection, provide training to perform regular self-examination, follow guidelines for skin checks, and offer referral to family members for genetic counselling as appropriate.[4]

If you would like to do a short case study on this topic, you can enrol in the Atypical melanoma – what’s new in diagnosis and management? activity on gplearning. Completion of the online activity is worth 2 CPD Activity points.

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Additional resources

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Suggested reading


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References

  1. Australian Cancer Network Melanoma Guidelines Revision Working Party. 2008. Clinical practice guidelines for the management of melanoma in Australia and New Zealand. Cancer Council Australia and Australian Cancer Network, Sydney and New Zealand Guidelines Group, Wellington. [Rescinded]
  2. Australian Institute of Health and Welfare. Australia’s health 2018. Australia’s health series no. 16. AUS 221. Canberra, ACT: AIHW, 2018. Available at https://www.aihw.gov.au [Accessed 7 February 2019]
  3. Cancer Australia. Optimal cancer care pathway for people with melanoma. Sydney, NSW: Cancer Council Australia, 2016. Available at https://www.cancer.org.au [Accessed 7 February 2019]
  4. Cancer Council Australia Melanoma Guidelines Working Party. Clinical practice guidelines for the diagnosis and management of melanoma. Sydney, NSW: Cancer Council Australia, 2016. Available at: https://wiki.cancer.org.au [Accessed 7 February 2019]
  5. Chamberlain A, Ng J. Cutaneous melanoma–atypical variants and presentations. Aust Fam Physician 2009;38(7):476–482.
  6. Curchin DJ, Harris VR, McCormack CJ, Smith SD. Changing trends in the incidence of invasive melanoma in Victoria, 1985–2015. Med J Aust 2018;208(6):265–269.
  7. Gershenwald JE, Scolyer RA, Hess KR, et al. AJCC Cancer Staging Manual. In: Amin MB, Edge S, Green F et al. 8th edn. Switzerland: Springer, 2017; p. 563–585.
  8. Mar VJ, Chamberlain AJ, Kelly JW, Murray WK, Thompson JF. Clinical practice guidelines for the diagnosis and management of melanoma: melanomas that lack classical clinical features. Med J Aust 2017;207(8):348–350.
  9. Mar V, Roberts H, Wolfe RS, English DR, Kelly J. Nodular melanoma: a distinct clinical entity and the largest contributor to melanoma deaths in Victoria, Australia. Journal of the American Academy of Dermatology 2013;68(4):568–575.
  10. Sinclair R. Skin checks. Aust Fam Physician 2012;41(7):464–469.
  11. Sladden MJ, Nieweg OE, Howle J, Coventry BJ, Thompson JF. Updated evidence-based clinical practice guidelines for the diagnosis and management of melanoma: definitive excision margins for primary cutaneous melanoma. Med J Aust 2018;208(3):137–142.
  12. Therapeutic Guidelines Limited. eTG July 2018 edition. West Melbourne, Vic:Therapeutic Guidelines Limited, 2018 [Accessed August 2018].
  13. The Royal Australian College of General Practitioners. Guidelines for preventive activities in general practice (‘The red book’). 9th edn. East Melbourne, Vic: RACGP, 2018.
  14. Watts CG, Cust AE, Menzies SW, Mann GJ, Morton RL. Cost-effectiveness of skin surveillance through a specialized clinic for patients at high risk of melanoma. J Clin Oncol 2017;35(1):63–71.
  15. Worsley R. Nine practice points from the new melanoma guidelines. Wollstonecraft , NSW, Melanoma Institute Australia 2016. Available at: https://www.melanoma.org.au

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