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Abstract

Background: Primary malignant melanoma (MM) of external ear accounts for a low proportion of cutaneous MM and its incidence in non-white females is very low. The stomach is a rare metastatic site for MM. Cases of gastric metastasis of external ear MM are extremely rare, of which the gene alterations and mechanism of metastasis are poorly understood. Case presentation: We report a 58-year-old Asian female patient who had a mass on the left auricle for 5 years and was diagnosed as nodular MM with BRAF V600E mutation after surgical resection. Postoperative metastases to the stomach and descending duodenum appeared one year later. After 11 months of BRAF-targeted therapy and immunotherapy, the patient was resistant to the drug and then died of systemic metastases to the brain, lungs, liver, left adrenal gland, and peritoneum. In addition to BRAF mutation, genetic testing showed aberrations of MYB, p16, MYC, and PTEN in this case. Conclusion: The clinical characteristics of external ear MM and gastric metastatic MM were summarized by retrospective study of the literature, respectively. Immunohistochemical staining is critical in the diagnosis of gastric metastasis from external ear MM, which often requires a multidisciplinary treatment approach, including surgery, targeted therapy and immunotherapy. We would like to provide some genetic information about the rare disease and discuss the appropriate treatment strategies for it. The present study suggested that the size of surgical margin, histological type of tumor and number of genetic aberrations may be closely associated with the metastasis potential, therapeutic efficacy and patient outcome.