30 HOW TO TREAT : MELANOMA
30 HOW TO TREAT : MELANOMA
3 NOVEMBER 2023 ausdoc . com . au
PAGE 28 minimally invasive , melanomas ( depth of invasion less than 0.8mm ) have a 10-year survival approaching 98 %, whereas melanomas thicker than 4mm are associated with , at best , 75 % survival at 10 years . 34 Thus , early detection of melanoma is critical .
Full skin examination is the standard of care for detection of all cutaneous malignancies . Dermatoscopy allows detailed examination of the colours and structures of naevi ( and other pigmented skin lesions ) that are not visible to the naked eye . Dermatoscopy aided skin checks , with appropriate training , provide improved diagnostic accuracy for melanoma and benign lesions . 35
Melanoma subtypes
The clinical presentation of cutaneous melanoma varies with melanoma subtypes . Based on clinical and histopathological features , cutaneous melanoma is categorised into the main subtypes listed in box 5 . 36
SUPERFICIAL SPREADING MELANOMA Superficial spreading melanoma ( SSM ) is the most common melanoma subtype , comprising about 55-60 % of all cutaneous melanomas . 37 SSM is more commonly seen in patients with high naevus counts and is associated with intermittent sun exposure . SSM can occur on any part of the body , but are commonly found on the back in men and the lower limbs in women . 37 SSM often presents as an ‘ ugly duckling ’ lesion that can be identified by the ABCDE characteristics ( Asymmetrical pigmented lesion , with irregular Borders , Colour variation , typically of larger Diameter that may be changing or Evolving ). 38 SSM displays a slow radial growth phase ( months to years ), with most ( more than 60 %) diagnosed at a Breslow thickness of 1mm or less , which are cured with wide local excision . 39
NODULAR MELANOMA Nodular melanoma ( NM ) is invariably characterised by invasion because of its pattern of early vertical growth . NM accounts for 10-15 % of all cutaneous melanomas , though contributes disproportionally to melanoma deaths . 38 The majority of NM lesions are greater than 2mm thick at the time of diagnosis . 40
NM lesions do not typically display the ABCD characteristics , instead presenting as Elevated , Firm and Growing ( EFG characteristics ) nodules , often on severely sun damaged skin ( for example , the head and neck of older patients ). 41 NM are often hypomelanotic and may mimic basal and squamous cell carcinomas .
LENTIGO MALIGNA MELANOMA Lentigo maligna melanoma comprises 10-15 % of cases of melanoma . 42 Lentigo maligna melanoma lesions typically arise as pigmented macules on chronically sun damaged skin of the head / neck / upper torso , and display a prolonged period of radial growth . 43 Lentigo maligna ( in situ tumour ) may be present for years before becoming invasive .
DESMOPLASTIC MELANOMA These are rare , accounting for only 1-2 % of cases of melanoma . 44 Desmoplastic melanoma can be exceptionally difficult to diagnose , as it
Figure 5 . Subungual melanoma in an 82-year-old woman .
Figure 6 . Melanoma biopsy under the microscope .
may present as amelanotic and have a scar-like appearance . Desmoplastic melanoma typically occurs on chronically sun damaged skin and may arise de novo , or in association with a pre-existing lentigo maligna . 45
ACRAL LENTIGINOUS AND SUBUNGUAL MELANOMA Acral lentiginous melanoma ( ALM ) may present on the soles of feet , palms of hands , or arise from the nail apparatus ( subungual melanoma , see
Figure 4 . Superficial spreading melanoma arising from a dysplastic naevus . The 4x8mm , pink-tan lesion with irregular borders at the upper left ( arrow ) is a dysplastic naevus .
Arising from it is an invasive malignant melanoma , with its characteristic blue-black colour , notched border and distorted surface .
The grey area at the lower left represents tumour regression .
US National Cancer Institute / bit . ly / 3YSfCr6
Wawjak / CC BY 4.0 / bit . ly / 3RWIV9P figure 5 ). ALM comprises less than 5 % of all melanomas , but is the most common melanoma subtype seen in patients with darker skin phototypes . 38 ALM typically presents as asymmetric macular pigmentation and
Box 5 . Melanoma subtypes
• Superficial spreading melanoma ( see figure 4 ).
• Nodular melanoma .
• Lentigo maligna melanoma .
• Desmoplastic melanoma .
• Acral lentiginous melanoma .
may form raised areas or undergo ulceration at more advanced stages of growth . Rarely , ALM may mimic benign lesions such as warts , calluses , ingrown toenails or fungal infections . 46
Clinically , subungual melanoma is characterised by longitudinal brown to black pigment that extends from the nail matrix to the distal nail plate . Pigmentation of the proximal or lateral nail fold is a sensitive clue to subungual melanoma ( Hutchinson ’ s sign ). 47 Subungual melanoma may be associated with nail destruction .
RED FLAG FEATURES Consider any lesion meeting the ABCD or EFG characteristics as suspicious for melanoma ; this requires a biopsy . The diagnosis of cutaneous melanoma can be challenging , particularly in hypopigmented lesions where a lack of pigment is significantly associated with poorer diagnostic accuracy . 48
Arguably , the most helpful clinical feature of cutaneous melanoma is that they are dynamic lesions . Consider a naevus that is new or changing in an adult suspicious for cutaneous melanoma , regardless of its other clinical features . Obtaining a history regarding the duration and possible change within a lesion is fundamental to the assessment of any potential skin cancer . The authors strongly recommend a diagnostic biopsy ( see figure 6 ) for any lesion that a patient has identified as ‘ different ’.
Histopathology
Histopathology is the gold standard for melanoma diagnosis . It is complex and varies according to melanoma subtype . Table 1 summarises the major histological features of different melanoma subtypes .
Differential diagnoses
Several cutaneous lesions may mimic melanoma ( see table 2 ). In many cases , melanoma cannot be ruled out on clinical and dermatoscopic examination alone . When melanoma is suspected , always perform a biopsy for histopathological examination .
Confirming the diagnosis
Melanoma requires histopathologic assessment for definitive diagnosis . Biopsy of lesions suspicious for melanoma should aim to remove the entire lesion for accurate diagnosis . In some circumstances , for example a large lesion on a site where complete excisional biopsy is impractical , partial biopsy may be appropriate .
EXCISIONAL BIOPSY Excisional biopsy of the complete lesion with a narrow ( 2mm ) peripheral margin , with depth of the procedure extending to fat , is the preferred biopsy technique for the diagnosis of melanoma . 57 Once the diagnosis has been made , re-excision of the lesion should be performed to achieve definitive treatment . Narrow peripheral margins on the initial diagnostic biopsy ensure potential