Acral melanoma presenting with multiple intussusceptions: a case report and literature review

Acral melanoma (AM) is a distinct subtype of melanoma unrelated to ultraviolet exposure, and its amelanotic variant presents considerable diagnostic challenges due to its occult clinical manifestations. Here, we report a rare case of amelanotic acral melanoma (AAM) with brain metastasis, initially presenting as multiple small intestinal intussusceptions. A 66-year-old male presented with abdominal pain and intestinal obstruction. Imaging revealed two sites of small bowel intussusception and space-occupying lesions in the brain. Emergency laparoscopic resection of three intestinal tumors was performed, and postoperative pathological examination confirmed metastatic melanoma. Positron emission tomography-computed tomography (PET-CT) suggested a suspicious primary lesion at the distal end of the right first metatarsal. Genetic testing revealed an activating KIT p.L576P mutation. Following multidisciplinary team discussion, the patient received palliative whole-brain radiotherapy combined with oral imatinib targeted therapy. One month after treatment, neurological function improved significantly, and imaging showed marked regression of the brain metastases. Three months post-treatment, follow-up PET-CT revealed no Fluorodeoxyglucose (FDG) uptake at the distal right first metatarsal. This case highlights the following: (1) Metastatic melanoma should be considered in the differential diagnosis of unexplained adult intussusception; (2) PET-CT is of significant value in detecting occult primary lesions; (3) Genetic testing should be performed in patients with acral melanoma to guide targeted therapy; (4) A multidisciplinary integrated diagnosis and treatment model combining local intervention for acute complications with systemic targeted therapy represents an effective strategy for advanced complex cases.