Six Cases of Amelanotic Melanoma: Focused on the Difficulty of Early Differential Diagnosis / 대한피부과학회지

ABSTRACT

Amelanotic melanoma comprises only 1.8~8.1% of malignant melanomas, and is difficult to diagnose clinically due to the lack of the diagnostic evidence of clinical pigmentation. To our knowledge, it is rarely reported, and only 10 cases have been reported in the Korean dermatological literature. It presents rather conflicting features such as a pink or red macule, papule, plaque, or nodule mimicking various benign and malignant conditions; therefore, it is difficult to diagnose. We performed a review of six patients with amelanotic melanoma focusing on differential diagnosis, particularly at the time of the initial visit. Clinical impressions included pyogenic granuloma, dermatofibrosarcoma protuberans, eccrine poroma, epidermal cyst, keloid, pilomatricoma, and squamous cell carcinoma in addition to malignant melanoma. The biopsy specimens were consistent with malignant melanoma with little or no melanin pigment on hematoxylin and eosin and Fontana-Masson stains. Four of the six patients were positive for S-100 and HMB-45, but two patients were positive for S-100 only. We report these cases to remind clinicians of the necessity of including malignant melanoma in the differential diagnosis process when patients show poor and unpredictable responses to treatment after a clinical diagnosis of other benign and malignant conditions.