Dermatology · Melanocytic Lesions
The facts most likely to be tested
Dysplastic nevi are atypical melanocytic nevi that serve as important clinical markers for an increased risk of developing cutaneous melanoma.
The classic clinical appearance of a dysplastic nevus includes asymmetry, irregular borders, variegated pigmentation, and a diameter typically greater than 6 mm.
Histopathologic examination reveals architectural disorder and cytologic atypia of melanocytes, often with bridging of nests and lamellar fibroplasia.
Patients with Familial Atypical Multiple Mole and Melanoma (FAMMM) syndrome possess a germline mutation in the CDKN2A gene and are at exceptionally high risk for melanoma.
The presence of multiple dysplastic nevi in a patient with a family history of melanoma warrants lifelong total body skin examinations and baseline clinical photography.
Prophylactic surgical excision is not indicated for all dysplastic nevi unless the lesion exhibits clinical evolution or histopathologic severe atypia.
Dermoscopic evaluation of a dysplastic nevus often demonstrates an atypical pigment network, irregular globules, or streaks that necessitate close monitoring or biopsy.
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A 34-year-old male presents for a routine skin check. He reports a family history of melanoma in his father and paternal aunt. Physical examination reveals a 7 mm pigmented lesion on his back with irregular, notched borders and variegated shades of brown and tan. The lesion is asymmetric and has not changed in size or color over the past year. Dermoscopy shows an atypical pigment network and irregular globules.
What is the most appropriate next step in management for this lesion?
Excisional biopsy
The lesion exhibits clinical and dermoscopic features of a dysplastic nevus; given the patient's significant family history and the lesion's size and irregularity, an excisional biopsy is required to rule out melanoma.
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Etiology / Epidemiology
Common in fair-skinned individuals with high cumulative UV exposure or genetic predisposition.
Clinical Manifestations
Features ABCDE criteria; asymmetry, irregular borders, and variegated color.
Diagnosis
Excisional biopsy is the gold standard for definitive histopathologic diagnosis.
Treatment
Complete surgical excision with clear margins is the definitive management.
Prognosis
Increased risk of malignant melanoma; requires lifelong dermatologic surveillance.
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Epidemiology & Etiology
Prevalence is highest in populations with Fitzpatrick skin types I-II. Genetic predisposition is linked to the FAMMM syndrome (Familial Atypical Multiple Mole Melanoma). Chronic UV radiation exposure serves as the primary environmental trigger for cellular mutation.
Pertinent Anatomy
These lesions typically arise at the dermo-epidermal junction. They are often larger than common acquired nevi, frequently exceeding 6 mm in diameter.
Pathophysiology
Dysplastic nevi represent a clonal proliferation of melanocytes with architectural and cytologic atypia. Mutations in the BRAF or NRAS genes are frequently identified. These lesions serve as both direct precursors to and markers of increased risk for malignant melanoma.
Clinical Manifestations
Lesions often exhibit a fried-egg appearance with a raised center and flat periphery. Use the ABCDE mnemonic: Asymmetry, Border irregularity, Color variation, Diameter >6mm, and Evolving morphology. Red flags include rapid change, bleeding, or ulceration, which mandate immediate biopsy to rule out melanoma.
Diagnosis
The excisional biopsy is the gold standard to assess architectural disorder and cytologic atypia. Shave biopsies are discouraged as they may result in incomplete sampling of the deep margins. Histopathology confirms the diagnosis by identifying bridging of nests and lamellar fibroplasia.
Treatment
For lesions with mild atypia, clinical observation may suffice if margins are clear. Moderate to severe atypia requires surgical excision with 2-5 mm margins to ensure complete removal. Do not use laser ablation or cryotherapy, as these destroy the tissue and prevent accurate histopathologic staging.
Prognosis
Patients with multiple dysplastic nevi have a significantly elevated lifetime risk of developing melanoma. Regular total body skin examinations are required, often every 6-12 months. Patients should be educated on strict photoprotection and self-monitoring.
Differential Diagnosis
Malignant Melanoma: exhibits rapid evolution and structural chaos
Common Acquired Nevus: typically uniform in color and <6mm
Seborrheic Keratosis: presents with a stuck-on waxy appearance
Dermatofibroma: demonstrates the dimple sign upon lateral compression
Solar Lentigo: flat, uniform brown macules related to sun damage