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ATYPICAL MELANOMA MIMICKING A VASCULAR TUMOR : CLINICAL AND DERMOSCOPIC FINDINGS

Introduction: Completely amelanotic melanomas are rare and therefore often misdiagnosed. Analysis of dermoscopic features of the vascular pattern appears to be a reliable method to suggest these particular diagnosis. Case Presentation: we report a case of an atypical primary cutaneous melanoma of plantar localization which clinically mimicked an angiomatous tumor. Clinical examination showed an angiomatous lesion of 10 cm long axis, located on the lateral part of the left sole. The two adjacent nodules measured 3 cm each, one was angiomatous and the other erythematous. There were also multiple left inguinal adenopathies. Dermoscopic evaluation of the lesion revealed the lack of a pigmented network and a rich vascular bundle made of polymorphous linear vessels, dotted vessels, white lines and milky red areas. The patient underwent excision of an angiomatous nodule. The definitive diagnosis was provided by immunohistochemistry (tumor cells expressed S100 and Melan A). . Brain and thoracic-abdominal-pelvic CT scan showed bilateral nodular lung involvement and a segment VI liver lesion. We concluded to the diagnosis of a primary amelanotic metastatic melanoma stage 4. Clinical Discussion: The term amelanotic refers to tumors that have no pigmentation on visual and dermoscopic inspection. Amelanotic and hypomelanotic melanomas are rare. They could mimic many benign and malignant tumors. There are three forms of AM. The papulonodular form represents 58% and could be misdiagnosed as a vascular tumor, which was the case of our patient. The contribution of dermoscopy is valuable in the clinical orientation in case of amelanotic melanoma. There is a correlation between the stage of the melanoma and the vascular pattern(s) observed as well as their distribution. The prognosis of amelanotic melanoma is characterized with a lower survival rate and a high risk of recurrence. The treatment of amelanotic melanoma is similar to the pigmented counterpart. Conclusion: In order to avoid therapeutic delay, melanoma should be considered whenever there is a suspicious plantar lesion even in the absence of pigmentation. Dermoscopy is a non-invasive technique that could help in the diagnosis.