Two unique cases of metastatic malignant melanoma of the gastrointestinal tract

INTRODUCTION AND IMPORTANCE: Gastrointestinal tract (GIT) is a common site for malignant melanoma metastasis, with small bowel being the most common. It is usually difficult to diagnose at an early stage because of the anatomical location of the disease. It is also challenging for pathologists to diagnose due to the small amount of biopsy samples. Survival rates of melanoma patients with distant metastasis are very poor. CASE PRESENTATION: This study presents two males, aged 67 and 69 years old, who have metastatic melanoma within the GIT. One was metastasis to the esophagus and another with metastasis to the jejunum presenting as intraluminal masses. Their clinical history and pathologic features of the metastasis are evaluated to give an insight into this disease. CLINICAL DISCUSSION: Gastrointestinal melanoma is hard to detect due to its anatomical location and limited ability to biopsy. Typically, they present at an advanced stage when diagnosed. Approximately 60 % of patients with cutaneous melanoma will have GIT metastasis at the time of autopsy. The small bowel was found to have an affinity for malignant melanoma due to the expression of the CCR9 ligand, CCL25. BRAF mutations are much less observed in GIT mucosal melanomas as compared to cutaneous melanomas. Furthermore, AKAP13-NTRK3 fusion has been reported specifically in the GIT mucosal melanomas. NTRK fusions in general can be observed in metastatic melanomas and have been reported in GIT metastatic melanomas. CONCLUSION: GIT malignant melanomas are difficult to detect due to their anatomical location, with poor prognosis, and have a unique genetic profile.