Amelanotic Melanoma on Fingertip: A Case Report

ABSTRACT

PURPOSE: Amelanotic melanoma represents a melanoma with an absence or a small number of melanin pigments and comprises 2% of all melanomas. These melanomas are frequently misdiagnosed, probably because of its nonspecific clinical features and difficulty in diagnosis, resulting in delayed diagnosis and treatment. We report a patient with amelanotic melanoma, who underwent surgical treatment with sentinel lymph node biopsy using gamma probe. METHODS: A 32-year-old female was presented with a slowly growing ill-defined, hypopigmented nonerythematous lesion with nail defect on right index finger tip. Preoperative punch biopsy was performed, showing an amelanotic melanoma. Sentinel lymph node biopsy was done using gamma probe(Crystal probe system, CRYSTAL PHOTONICS GmbH, Germany) and confirmed no evidence of regional lymph node metastases. The patient underwent amputation at the proximal interphalangeal joint. RESULTS: Histopathologic findings showed superficial spreading melanoma. There were no melanin pigments in Hematoxylin & Eosin stain but positive immunohistochemical stainings for S-100 protein and Hmb45, which were consistent with amelanotic melanoma. Patient's postoperative course was uneventful without any complication and had no evidence of recurrence of tumor in 6 months follow-up period. CONCLUSION: Amelanotic melanoma is extremely rare subtype of malignant melanoma with histopathologic findings of atypical melanocytes without melanin pigments. Early detection is crucial since survival is strongly related to tumor thickness and tissue invasion at the time of diagnosis. Wide excision is the treatment of choice and other conjunctive therapy has not been successful.