Dermatology · Skin Cancer
The facts most likely to be tested
The most important prognostic factor for survival in localized melanoma is the Breslow thickness, which measures the depth of invasion in millimeters.
The ABCDE criteria (Asymmetry, Border irregularity, Color variation, Diameter >6mm, and Evolving) are the clinical hallmarks used to screen for suspicious pigmented lesions.
Superficial spreading melanoma is the most common histologic subtype and typically presents with a radial growth phase.
Nodular melanoma is characterized by rapid vertical growth and a poor prognosis due to early dermal invasion.
Acral lentiginous melanoma is the most common subtype in patients with darker skin tones and typically presents on the palms, soles, or under the nails.
The initial diagnostic procedure of choice for a suspicious lesion is an excisional biopsy with narrow margins to allow for accurate histopathologic staging.
Sentinel lymph node biopsy is indicated for patients with a Breslow thickness >0.8 mm or the presence of ulceration to determine the need for systemic staging and adjuvant therapy.
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A 54-year-old male presents to the clinic for evaluation of a changing lesion on his back. He reports that the lesion has grown in size over the last six months and has developed irregular borders and variegated colors including shades of brown, black, and blue. On physical examination, the lesion is a 9 mm asymmetric macule with a notched border. There is no palpable lymphadenopathy.
What is the most appropriate next step in the management of this patient?
Excisional biopsy
The patient's lesion meets the ABCDE criteria for melanoma, and an excisional biopsy is the gold standard for diagnosis and determining the Breslow thickness, which is the most important prognostic factor.
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High yield triage
Etiology / Epidemiology
Driven by UV radiation exposure and genetic predisposition (e.g., BRAF mutations). Highest incidence in fair-skinned individuals with history of blistering sunburns.
Clinical Manifestations
Follow the ABCDE criteria. Look for asymmetry, irregular borders, and color variegation in a changing pigmented lesion.
Diagnosis
Excisional biopsy is the gold standard. Breslow depth is the most important prognostic factor for survival.
Treatment
Wide local excision is the primary treatment. Do not perform shave biopsy as it precludes accurate depth measurement.
Prognosis
Survival is determined by Breslow depth. Lesions >1.0 mm require sentinel lymph node biopsy.
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Epidemiology & Etiology
Incidence is rising, with UV exposure (especially intermittent, intense exposure) being the primary environmental trigger. Risk is significantly elevated in patients with dysplastic nevus syndrome or a family history of melanoma. Fair skin, light hair, and a high total nevus count are major clinical risk factors.
Pertinent Anatomy
Melanoma arises from melanocytes located at the dermo-epidermal junction. The depth of invasion into the papillary and reticular dermis dictates the metastatic potential and staging.
Pathophysiology
Malignant transformation often involves activating mutations in the BRAF V600E gene, leading to uncontrolled cell proliferation. The tumor progresses from a radial growth phase (horizontal spread) to a vertical growth phase (invasion into deeper dermis), which correlates with the risk of hematogenous spread.
Clinical Manifestations
Use the ABCDE mnemonic: Asymmetry, Border irregularity, Color variation, Diameter >6mm, and Evolution (change in size/shape/color). Red flags include bleeding, ulceration, or pruritus in a pre-existing mole. The nodular subtype is particularly aggressive and may present as a rapidly growing, dome-shaped, blue-black papule.
Diagnosis
The gold standard is a full-thickness excisional biopsy with narrow margins. Breslow depth (measured in mm from the granular layer to the deepest tumor cell) is the single most important prognostic variable. Sentinel lymph node biopsy is indicated for lesions >1.0 mm or those with high-risk features like ulceration.
Treatment
Primary management is wide local excision with margins determined by the Breslow depth (typically 1-2 cm). Shave biopsy is contraindicated because it prevents accurate staging. Advanced or metastatic disease may require immunotherapy (e.g., pembrolizumab) or targeted therapy (e.g., vemurafenib) for BRAF-positive cases.
Prognosis
Prognosis is inversely proportional to Breslow depth. Patients require lifelong dermatologic surveillance due to the high risk of recurrence and development of secondary primary melanomas.
Differential Diagnosis
Seborrheic keratosis: 'stuck-on' appearance with horn cysts
Dysplastic nevus: irregular borders but stable over time
Basal cell carcinoma: pearly papule with telangiectasias
Pyogenic granuloma: friable, vascular papule often following trauma
Atypical mole: requires monitoring but lacks rapid evolution