A Case Report: Primary Malignant Melanoma of the Jejunum

Background: Malignant melanoma represents only less than 3% of all malignant tumors in the gastrointestinal (GI) tract. Differentiating primary melanomas from metastatic melanoma can be difficult. Case Presentation: We report the case of a 60-year-old woman who presented with signs of intestinal obstruction. An USG abdomen and KUB shows intussusception small bowel, and CT imaging revealed a mass in the proximal small intestine. Emergency laparotomy was performed, which identified an intraluminal tumor in the proximal jejunum. This tumor was surgically resected, followed by end-to-end anastomosis. Histopathological and immunohistochemical analyses confirmed malignant melanoma, with tumor cells testing positive for S-100, HMB-45, and Melan-A. A comprehensive postoperative evaluation including whole-body PET-CT, dermatological, ophthalmological, and nodal assessments showed no evidence of a primary cutaneous, mucosal, ocular, or nodal lesion, nor any additional metastases. These findings supported the diagnosis of primary jejunal melanoma, an exceedingly rare condition. Outcome: The patient recovered without complications and was referred to medical oncology. She began adjuvant immunotherapy with nivolumab. At the 6-month follow-up, she remained clinically asymptomatic, with no evidence of recurrence observed in surveillance imaging. Conclusion: In rare but significant instances of small intestinal obstruction, primary malignant melanoma of the small intestine is taken into consideration. The best results can only be obtained with early surgical intervention, a precise histological diagnosis, and prompt immunotherapy treatment.