Solid serous adenoma of the pancreas: Clinicopathologic features and differential diagnosis

We discuss the clinical, radiologic, and pathologic features, as well as the differential diagnosis, of pancreatic solid serous adenomas. Solid serous adenoma is a rare variant of the serous cystic neoplasms of the pancreas, with only 11 cases reported in the literature. Preoperatively, this lesion is frequently misclassified as a well-differentiated pancreatic endocrine neoplasm because of its well-circumscribed, solid, and vascular appearance on imaging studies. The primary diagnostic challenge for the surgical pathologist is to distinguish solid serous adenoma from other neoplasms with clear cytoplasm, including primary ductal adenocarcinoma with clear cell or foamy gland change, well-differentiated pancreatic endocrine neoplasm with clear cell features, metastatic clear cell renal cell carcinoma, PEComa, and solid-pseudopapillary neoplasm with clear cell change. A periodic acid-Schiff with and without diastase digestion demonstrates cytoplasmic glycogen, and immunohistochemical labeling for markers such as CD10, CD56, synaptophysin, chromogranin, renal cell carcinoma-Ma, and β-catenin can be useful in excluding other entities in the differential diagnosis. Establishing the correct diagnosis is particularly important because the solid serous adenoma is a benign lesion with much better prognosis than the other lesions in the differential diagnosis.