Amelanotic Malignant Melanoma: A Case Report And Literature Review

Background: Malignant melanoma is a highly malignant tumor with early metastasis and poor prognosis. Therefore, early diagnosis is very important. Amelanotic malignant melanoma is a rare type of malignant melanoma. It is often misdiagnosed as other cutaneous diseases or tumors due to the lack of melanin and various clinical manifestations. Early diagnosis of amelanotic melanoma is often very difficult.Case presentation: A 39-year-old male was admitted to the department of dermatology for some red nodules and plaques in his head for two years. He had been diagnosed as"epidemal cyst"and accepted laser treatment in the local hospital, but original lesions increased and expanded to form a plaque two months later. Then he accepted surgery treatment without biopsy. Three months later, the local lesions recurred again. Antibiotics creams, antifungal agents, and corticosteroids had all been used topically, but gained no obvious effect. The red plaques expanded and became confluent, with an ulcer in the center and some crusts on the surface. Physical examination revealed several red and irregular nodules on the head. Painless lymph nodes could be touched on the neck and back of left ear. CT exzamnation of lung revealed metastasic lung cancer.Histopathologic examination revealed diffusive infiltration of tumor cells in the dermis and nests of tumor cells in the dermis and dermoepidermal junction. The tumor cells are of different sizes and shapes, with large nucleus and obvious heteromorphism. No obvious melanin was observed in the tumor cells.The tumor cells are positively stained by S-100 and melan-A. The final diagnosis was amelanotic malignant melanoma. The patient refused teatment in our hospital after the diagnosis, and we lost the follow up. Conclusion: Amelanotic malignant melanoma is often misdiagnosed due to the lack of melanin and various clinical manifestations.The histopathological and immunohistochemical examinantion are necessary for suspicious cases. Some improper treatment should be avoided before the diagnosis was quite clear.