Answer: Serous cystadenoma

Histology: This lesion is designated by a variety of names including serous cystadenoma, glycogen rich adenoma, and microcystic adenoma. Because these lesions are often composed of larger cysts, we prefer the term serous cystadenoma. Lining the large cysts are flattened epithelium with benign appearing nuclei and clear cytoplasm. In areas, the lesion develops small papillae lined by similar cells. The cysts are separated by a fibrous septae of varying thickness.

Discussion: Solid-cystic-papillary epithelial neoplasms of the pancreas are cystic as a result of cystic degeneration. They are much more cellular, consisting of sheets of uniform round to oval cells with areas of necrosis generating the cysts and papillary structures. They are often accompanied by areas of hemorrhage, foam cells, and sometimes by giant cells. Mucinous cystadenomas are analogous to their ovarian counterparts. The columnar cells contain abundant mucin and may form papillary formations. Often, the underlying stroma is cellular resembling ovarian stroma. A lymphangioma may bear superficial resemblance to serous cystadenoma. However, whereas some of the cysts in serous cystadenoma are lined by flattened epithelium that could resemble endothelial cells, others are more overtly epithelial with a more columnar appearance and papillary formation.