[Serous microcystic adenoma of the pancreas: cytologic and histologic features]

Cytologic and histologic features in a case of serous microcystic adenoma of the pancreas in a 61-year-old female are presented. In fine-needle aspiration materials, epithelial cells arranged singly, in small clusters and in monolayer sheets were found. The neoplastic cells had round to oval nuclei with finely distributed chromatin and inconspicuous nucleoli. Nuclear atypia and mitoses were not seen. The cytoplasm was moderately abundant and finely granular. Histologically, the encapsulated tumor was composed of multiple small cysts lined by a single layer of flat to cuboidal cells. The tumor cells contained clear cytoplasm with glycogen and centrally located round to oval nuclei with inconspicuous nucleoli without any atypia. Mitoses were absent. The intervening stromal septa were hypocellular. Immunohistochemically, the tumor cells revealed diffuse positivity of cytokeratins and epithelial membrane antigen. Proliferative antigen Ki-67 was positive only in sporadic cells. No immunoreactivity for vimentin, carcinoembryonal antigen and S-100 protein was found. Chromogranin A and synaptophysin were expressed only in Langerhans' islets in the tumor capsula. In differential diagnosis, it is important to distinguish serous microcystic adenoma mainly from lymphangioma, cavernous hemangioma, serous cystadenocarcinoma, mucinous cystadenoma or cystadenocarcinoma, solid and pseudopapillary epithelial tumour, acinar cell cystadenocarcinoma, renal cell carcinoma and mesothelioma.