Mixed acinar-endocrine carcinoma arising in the ampulla of Vater.

We present a case of mixed acinar-endocrine carcinoma arising in the periampullary region of the duodenum. The patient was a 78-year-old male with a periampullary mass diagnosed during upper endoscopy. On gross dissection, the mass was 2.3 cm in diameter, noncystic, and confined to the duodenal submucosa. Microscopically, the tumor formed nests that were positive for amylase, trypsin (weakly), and synaptophysin (diffusely). Ultrastructurally, the tumor had 2 populations of granules with mean diameters of 175 nm and 540 nm, consistent with endocrine and zymogen granules, respectively. These studies were consistent with a mixed acinar-endocrine carcinoma that arose in the duodenum. A review of the literature revealed 1 report of an acinar cell carcinoma arising in jejunal pancreatic heterotopia. The present article is the first reported case of an acinar cell carcinoma arising in the periampullary region of the duodenum, possibly in a focus of pancreatic heterotopia.