A patient, aged 56 years, presented for evaluation of an erythematous, slightly raised plaque of her right calf. The patient’s mother was diagnosed with melanoma at age 45 years.
The patient complained of mild pruritus of the affected area. Inguinal nodes were not palpable. Full body examination was otherwise unremarkable.
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Biopsy of the lesion revealed an amelanotic melanoma, an uncommon subtype of melanoma with an incidence of 2% to 8%. 1
Amelanotic melanoma typically affects individuals aged 65 years and older with a male predominance. 2 Two major risk factors in the development of this condition are chronic outdoor sun exposure and sun damaged skin.
Amelanotic melanoma characteristically presents as a skin colored lesion with no or scant pigmentation and can arise as an erythematous, scaly patch or plaque with an irregular border. 3, 4 The neoplasm often resembles other benign dermatologic conditions, including dermatitis, seborrheic keratosis, granuloma annulare, and pyogenic granuloma, which can lead to a delay in diagnosis. 1, 5 The condition can also mimic superficial basal cell carcinoma, Bowen disease, and keratoacanthoma. 1, 6
Given the lack of pigment, clinical recognition of amelanotic melanoma requires a high degree of suspicion. Dermoscopy is an in vivo technique that affords the clinician enhanced visualization of skin lesions. Under the dermatoscope these lesions may reveal traces of pigmentation as well as an irregular vascular pattern. 4, 7
Definitive diagnosis is made by biopsy. Patients diagnosed with amelanotic melanoma have a lower five year survival rate than those with superficial spreading melanoma in large part attributable to delay in recognition. 2
Megha Patel, BS, is a medical student at the Commonwealth Medical College.
Stephen Schleicher, MD, is an associate professor of Medicine at the Commonwealth Medical College and an Adjunct Assistant Professor of Dermatology at the University of Pennsylvania Medical College. He practices dermatology in Hazleton, PA.
- Kosh SE, et al. J Am Acad Dermatol. 2000; 42: 731-734.
- Moreau JF, et al. Melanoma Research. 2013; 23:408-413.
- Maier T, et al. Journal of the European Academy of Dermatology and Venerology. 2013; 27: e42-e52. doi: 10.1111/j.1468-3083.2012.04465.x
- Pizzichetta MA et al. British Journal of Dermatology. 2004; 150:1117-1124. doi: 10.1111/j.1365-2133.2004.05928.x
- McClain SE. International Journal of Dermatology. 2012; 15: 420-426.
- Lunardon L et al. International Journal of Dermatology. 2013; 52: 1019-1032.
- Steglich RB1, et al. An Bras Dermatol. 2012 Nov-Dec;87(6):920-3.