Serous Microcystic Adenoma of the Pancreas

Abstract

75-year-old woman presented with a 2-week history of diffuse abdominal pain and emesis. According to the patient, the pain was dull and relieved by vomiting. She was admitted for a possible small bowel obstruction. A computed tomographic (CT) scan revealed a large vascular tumor in the distal pancreas that was inhomogeneous and suggestive of multiple, very small cysts. No other masses were visualized in the abdomen, and no lymphadenopathies were present. The patient’s medical history was significant for diabetes mellitus, atrial fibrillation, and coronary artery disease. Her social history was negative for smoking and drinking. A distal pancreatectomy and splenectomy were performed. The specimen consisted of a portion of distal pancreas and a spleen. Most of the pancreatic tissue received was replaced by a slightly bosselated mass measuring 9 cm in greatest dimension (Figure 1). Only a 1.5-cm segment of normal pancreas was present. The mass appeared to be well circumscribed with no invasion of the splenic vessels or the spleen. The cut sections of the mass showed a central scar with radiating fibrous bands. A closer inspection revealed multiple small cysts ranging in size from less than 0.1 to 0.5 cm. Microscopically, the tumor was composed of multiple cysts containing proteinaceous fluid that were lined by low cuboidal cells with centrally located nuclei and clear cytoplasm (Figure 2). Nuclei were round and had inconspicuous nucleoli. The cells lacked atypia, and there were no mitoses present. Focal areas of intracystic papillary projections were also present. At the periphery and within the fibrous stroma, blood vessels were identified, explaining the vascular appearance of the tumor on CT. The cells contained periodic acid‐Schiff‐positive granules (Figure 3), which were digested by diastase, indicating the presence of intracytoplasmic glycogen. Five peripancreatic lymph nodes showed no evidence of malignancy. A diagnosis of serous microcystic adenoma (SMA) was rendered. Serous microcystic adenomas are benign tumors of the pancreas and are also known as glycogen-rich cystadenomas or serous cystadenoma. 1,2 Two thirds of patients present with symptoms such as abdominal pain, abdominal mass, nausea, vomiting, or weight loss. The remaining one third of the tumors are discovered incidentally on rou