Isolated pancreatic metastasis from malignant melanoma: a case report and literature review

Isolated pancreatic metastasis from malignant melanoma is rare. Pancreatic metastasis is difficult to diagnose in patients with unknown primary malignant melanoma. Endoscopic ultrasound-guided fine-needle aspiration plays an important role in confirming the diagnosis. A 67-year-old woman was referred to our institution because of a mass in her pancreas. Computed tomography and magnetic resonance imaging revealed a 35-mm mass localized on the pancreatic tail, with low attenuation, surrounded by a high-attenuation rim. Endoscopic ultrasonography revealed a hypoechoic mass with central anechoic areas. Endoscopic ultrasound-guided fine-needle aspiration of the mass was performed, and the pathological diagnosis was malignant melanoma. Intense fluorodeoxyglucose uptake was observed in the pancreatic tail on positron emission tomography–computed tomography. No other malignant melanoma was found. Distal pancreatectomy was performed. Six months postoperatively, positron emission tomography–computed tomography revealed high uptake in the left nasal cavity, and biopsy revealed the mass to be a malignant melanoma, indicating that the primary site of the malignant melanoma was the left nasal cavity and that the pancreatic mass and peritoneal lesion were metastases. The patient had survived > 2 years after the distal pancreatectomy. Pancreatic resection of isolated pancreatic metastasis can possibly prolong survival; however, metastatic melanoma usually has poor prognosis.