Pancreatic metastasis of Merkel-cell carcinoma: a rare neoplasm of the pancreas.

Only 2-3.9% of pancreatic malignancies represent metastases from other sites, the most common origins being the lungs, kidneys, and gastrointestinal tract. Differentiating between primary and secondary lesions may be challenging with imaging techniques but EUS-guided FNA is a safe, accurate procedure for obtaining a tissue diagnosis. We report the case of a 70-year-old male who, following satisfactory treatment for a Merkel-cell carcinoma in the right groin, presented with jaundice and an indurated, vascularized, adherent nodule on the right thigh. Endoscopic ultrasound identified a mass at the pancreatic head as well as a perilesional adenopathy with no evidence of vascular involvement. FNA revealed cell proliferation, which was immunohistochemically positive for CD56, synaptophysin, and chromogranin, these findings being consistent with poorly-differentiated neuroendocrine carcinoma. Given the patient's history we considered this lesion to be a pancreatic metastasis of Merkel-cell carcinoma, which represents a rare finding.