Melanoma subtypes, Breslow depth and urgent referral

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Melanoma is a malignant melanocytic tumour with subtype-dependent growth. Document site, evolution, dimensions, surface, ulceration and the patient’s background mole pattern. Examine the full skin and regional nodes with consent. Amelanotic lesions may look pink, red or skin-coloured, and acral lesions may be overlooked when clinicians assume melanoma must occur on pale sun-exposed skin.

Subtype suggests a route to recognition but does not replace histology. Superficial spreading has a radial phase; nodular disease gains thickness quickly; lentigo maligna melanoma arises in chronically sun-damaged skin; acral lentiginous disease affects palms, soles and nails. Desmoplastic melanoma may be an inconspicuous scar-like nodule and needs expert pathology because pigment can be sparse.

Breslow depth links primary histology to wide-excision margins, sentinel-node discussion, imaging and follow-up. The pathology report also records ulceration, mitotic activity and margins and may include microsatellites and subtype. Partial or superficial biopsy can transect the deepest tumour and underestimate thickness, so specialist planning is essential when complete excision is anatomically difficult.

Key points

Superficial-spreading melanoma often evolves as an irregular multicoloured macule or plaque; nodular melanoma is elevated, firm and rapidly growing and may be uniformly coloured.
Lentigo maligna melanoma develops within a slowly enlarging irregular macule on chronically sun-damaged head or neck; invasion may arise after a prolonged in-situ phase.
Acral lentiginous melanoma affects palms, soles or nail units and must be considered in every skin tone; delayed recognition contributes to thicker presentation.
Refer a lesion urgently when the weighted seven-point score is 3 or more, dermoscopy suggests melanoma, or strong nodular, acral, nail or ugly-duckling concern exists.
The diagnostic standard is complete full-thickness excision biopsy with a narrow clinical margin where feasible, oriented so Breslow depth and ulceration can be measured.
Breslow thickness is the vertical distance in millimetres from the top of the granular layer, or ulcer base, to the deepest invasive melanoma cell.
Do not confuse diagnostic excision with definitive wide local excision; the latter margin is chosen after histological stage is known.
Palpable nodes or systemic symptoms require specialist staging, but a normal node examination does not exclude microscopic spread.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Intermittent ultraviolet injury

Intense intermittent ultraviolet exposure and sunburn, especially earlier in life, contributes to many superficial-spreading and nodular melanomas on intermittently exposed skin.

Chronic cumulative ultraviolet exposure

Long-term cumulative sun damage is associated with lentigo maligna melanoma on older, chronically exposed facial skin.

Genetic and naevus susceptibility

Numerous or atypical naevi, previous melanoma, family history and inherited variants increase risk but are absent in many patients.

Acral and mucosal pathways

Acral and mucosal melanomas have distinct molecular patterns and are not explained chiefly by ultraviolet exposure; they occur in every skin tone.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Radial growth
Atypical melanocytes initially spread within epidermis and superficial dermis, producing an enlarging irregular macule or thin plaque in many subtypes.
2
Vertical invasion
Dermal invasion creates thickness and access to lymphatic and blood vessels; nodular melanoma may enter this phase early with little radial warning.
3
Ulceration
Loss of overlying epidermis reflects biologically important tumour behaviour and independently worsens pathological staging and prognosis.
4
Lymphatic and haematogenous spread
Tumour cells can reach regional nodes, in-transit skin, lung, liver, brain, bone and other organs as stage advances.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Superficial-spreading pattern

An enlarging asymmetric macule or thin plaque has irregular border and several uneven colours, often on trunk or limb.

Nodular patternRed flag

A firm elevated lesion grows continuously over weeks to months and may be black, brown, red or skin-coloured.

Lentigo maligna pattern

A slowly expanding irregularly pigmented facial macule on photodamaged older skin develops new thickening when invasion occurs.

Acral lentiginous patternRed flag

An irregular palm or sole patch or broad changing longitudinal nail band may extend pigment onto adjacent nail-fold skin.

Amelanotic melanoma

A persistent growing pink-red nodule or plaque may ulcerate or bleed despite lacking the colour cues in ABCDE.

Nodal or in-transit diseaseRed flag

A firm draining-basin node or new dermal nodules between scar and nodal basin suggests regional spread and requires urgent oncology assessment.

Red flags requiring action

Rapid nodular growth, ulceration, spontaneous bleeding, acral or nail-unit evolution, palpable nodes, neurological or systemic metastatic symptoms, or a lesion scoring 3 or more on the weighted seven-point checklist requires urgent cancer-pathway assessment.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Specialist dermoscopyFirst step
Why
Identify melanoma-specific pigment, vascular, acral and nail structures and choose the biopsy plan.
Interpretation and limitations
Suspicious dermoscopy prompts histology; a bland image cannot override convincing evolution or a rapidly growing nodule.
02
Full-thickness excision biopsy
Why
Establish diagnosis, Breslow depth, ulceration and margins while preserving architecture.
Interpretation and limitations
Use a narrow clinical margin and include subcutaneous fat where feasible; avoid curettage and superficial shave for suspected invasive melanoma.
03
Histopathology report
Why
Define subtype, invasive depth, ulceration, mitoses, margin status and other staging features.
Interpretation and limitations
Breslow is measured to the deepest invasive cell; a transected deep margin may prevent accurate staging and require expert review.
04
Regional node examination and ultrasound
Why
Assess clinical or specialist-defined risk of regional metastasis.
Interpretation and limitations
Suspicious nodes require ultrasound-guided sampling; sentinel-node biopsy addresses clinically occult staging in selected patients.
05
Stage-directed imaging and molecular testing
Why
Detect metastatic disease and identify treatment-relevant variants when indicated.
Interpretation and limitations
Imaging is not automatic for every thin melanoma and follows stage, symptoms and multidisciplinary guidance.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Atypical melanocytic naevus

A longstanding stable asymmetric naevus can resemble melanoma, but evolution and a lesion unlike the patient’s signature pattern demand histological assessment.

Seborrhoeic keratosis

A waxy stuck-on lesion with milia-like cysts may be pigmented, while irritated or clonal lesions can remain diagnostically uncertain.

Pigmented basal-cell carcinoma

A shiny or ulcerated papule with arborising vessels and blue-grey structures can mimic melanoma and also requires cancer assessment.

Subungual haemorrhage

Traumatic blood usually migrates distally with nail growth and lacks progressive periungual pigmentation, but uncertainty warrants nail-specialist review.

Amelanotic malignancy

Pink-red melanoma, SCC and pyogenic granuloma can overlap; a persistent enlarging bleeding nodule needs biopsy even without pigment.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Suspicious primary lesionRefer intact for diagnosisFirst stepClinical or dermoscopic features, evolution, nodular growth or acral or nail change raises melanoma concern.

1Make an urgent suspected-cancer referral with precise site, size, evolution and risk information and suitable consented images if locally supported.
2Leave the lesion intact for specialist dermoscopy and complete full-thickness excision biopsy unless an agreed expert pathway directs otherwise.
3Explain the difference between suspicion and diagnosis, track attendance and safety-net rapid change, bleeding or new nodes.

02Confirmed melanomaStage from pathologyHistology confirms in-situ or invasive cutaneous melanoma.

1Review Breslow depth, ulceration, margins, subtype and pathological stage in the specialist multidisciplinary team.
2DefinitivePlan definitive wide local excision and discuss sentinel-node staging according to depth and adverse features.
3Assess nodes and symptoms, order stage-directed imaging and molecular tests where indicated and provide a written follow-up plan.

03Possible recurrenceEscalate new scar, node or systemic symptomsEscalationA melanoma survivor develops a changing scar nodule, in-transit lesion, regional node or concerning organ symptom.

1Arrange urgent specialist assessment and document timing, site, neurological, respiratory, bone and constitutional symptoms.
2Use targeted imaging and image-guided or skin biopsy to establish recurrence without delaying care for neurological emergencies.
3Return results through the melanoma multidisciplinary pathway and coordinate systemic, surgical, radiotherapy and supportive options.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Regional nodal metastasis

Lymphatic dissemination can present as a firm regional node, microsatellite, satellite lesion or in-transit dermal nodule between primary and nodal basin.

Distant metastatic disease

Brain, lung, liver, bone and soft-tissue metastases cause focal neurological symptoms, breathlessness, pain, weight loss or organ dysfunction.

Treatment morbidity

Wide excision, nodal surgery, immunotherapy and targeted therapy can cause wound, lymphatic, immune-mediated and organ-specific adverse effects.

Second primary melanoma

A survivor remains at increased risk of another primary lesion, making self-examination and risk-stratified professional surveillance important.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Ensure the pathology report includes measurable Breslow depth or explains why transection prevents it, plus ulceration and margins.
After treatment, teach monthly self-examination of skin and regional nodes without encouraging compulsive daily checking.
At specialist follow-up, examine the scar, in-transit pathway, nodal basins and full skin and ask stage-relevant systemic symptoms.
Use consented total-body or lesion photography in selected high-naevus-burden patients within an owned surveillance pathway.
Provide rapid re-entry instructions for a new changing lesion, scar nodule, node, persistent headache, focal neurology or unexplained weight loss.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Thickness drives consequence

A small-diameter nodular lesion can already be thick, making speed of vertical growth more important than width.

Ulcer base changes origin

When epidermis is ulcerated, Breslow measurement begins at the ulcer base rather than the missing granular layer.

Acral is not ultraviolet shorthand

Palm, sole and nail melanoma biology differs and prevention messaging must not imply that sun avoidance removes all risk.

Excision has two stages

Narrow diagnostic excision obtains staging, while later wide excision uses a stage-determined clinical margin.

Pink can be melanoma

Amelanotic disease requires attention to persistent growth, firmness, ulceration and atypical vessels rather than pigment alone.

11Common pitfallsFrequent interpretation and management errors.

01
Using diameter below 7 mm to dismiss a rapidly growing nodular melanoma.
02
Performing curettage or superficial shave and losing reliable Breslow depth.
03
Assuming a dark-skinned patient cannot develop melanoma and omitting acral and nail examination.
04
Interpreting a normal node examination as exclusion of microscopic regional disease.
05
Giving a melanoma diagnosis before histology rather than explaining suspicion and urgent next steps.