Metastatic Melanoma of Uncertain Primary with 5-Year DurableResponse after Conventional Therapy: A Case Report withLiterature Review

A 51-year-old Thai woman presented with bilateral leg edema and painful left inguinal mass for 6 months. Physical examinationrevealed matted bilateral inguinal lymph nodes up to 9 cm in size. Otherwise, physical examinations including skin wereunremarkable. The result of the lymph node incisional biopsy is consistent with that of metastatic melanoma. The extensiveinvestigation demonstrated multiple intra-abdominal and inguinal lymph nodes without detectable primary tumor. Palliativeradiation and conventional chemotherapy were prescribed. The CT scan between treatments showed that the response wasstable disease, but the following CT scan demonstrated a gradual decrease in size from August 2012 to November 2017including the lesions outside radiationfields. Moreover, she developed vitiligo during a follow-up visit. The previous datareported the median overall survival among the patients who were treated with conventional chemotherapy ranging from 9.1 to9.3 months and whose 5-year survival was less than 10%. This case represented a metastatic melanoma of unknown primarywho achieved a durable response by conventional treatment. The clinical features including nodal-only disease, vitiligo, andabscopal effect of radiation were considered to be the favorable factors.