Serous Adenoma of the Pancreas With Multiple Microcysts Communicating With the Pancreatic Duct

The rare neoplastic cystic adenomas of the pancreas form two groups of tumors: macrocystic mucinous and microcystic serous adenomas. Both entities show specific radiologic and histologic features. Several recent case reports, however, suggest some diversity within the group of microcystic serous adenomas. We present the case of a young man operated because of epigastric pain for 12 months and a palpable microcystic tumor of the pancreatic head. Multiple cysts communicating with branches of the pancreatic duct in an alveolar-like pattern were demonstrated on endoscopic retrograde cholangiopancreatography. Histologic examination of the specimen confirmed the diagnosis of a serous adenoma of the pancreas. The tumor morphology in this case may suggest a ductal origin of microcystic serous adenomas.


INTRODUCTION
In 1962 Campbell and Cruickshank [2] proposed to distinguish cystic pancreatic tumors with large cysts containing mucous from microcystic tumors with no evident mucous. This classification was reconfirmed again by Compagno and Oertel in 1978 [3] on a series of 34 cases: (1) a group of tumors with a single or multiple macrocysts (>20 mm) lined by mucin-producing cells called mucinous cystadenoma or macrocystic adenoma (MCA) and (2) microcystic We report a case of SCA where multiple adenomas have been reported only twice so far microcysts communicated with branches of the [8,20]. Serous cystadenoma usually occurs in the main pancreatic duct. The unusual tumor middle-aged woman with a history of epigastric morphology in this case may again raise the pain and a palpable epigastric mass in a quarter of question of the cellular origin of SCA. cases. It is frequently associated with diabetes mellitus, cholecystolithiasis and benign or malignant, extra-or intra-pancreatic tumor growth [13].
CASE REPORT Both entities show specific radiologic and histologic features. The tumor and cyst size A 36-year-old Turkish man was admitted bemay be determined by either ultrasound (US) or cause of a palpable epigastric mass and a history computed tomography (CT). On endoscopic of sporadic epigastric pain for 12 month. retrograde cholangiopancreatography the main Physical examination and upper intestinal enpancreatic duct (MPD) usually appears normal doscopy had repeatedly been without patholoor compressed by a SCA. A communication gical findings and blood chemical values had between cysts and the MPD is suggestive of been normal several times until finally an MCA or other cystic lesions of the pancreas, abdominal CT scan revealed a inhomogenic Over the years several case reports, however, tumor of the pancreatic head 1 week prior to suggest some morphologic diversity within the admission. group of serous cystadenomas. Lewandrowski On admission a large tender epigastric mass et al. [15] and Mori et al. [16] describe a serous was palpated. Physical examination was othercystadenoma of the pancreas bearing cysts wise normal. The patient denied nausea or larger than 20mm. Egawa et al. [4] observed vomiting, recent weight loss, jaundice, dark serous ill-defined tumors of the pancreatic head urine, changes in bowel habits, former pancreaextending into the pancreatic parenchyma titis or any other major diseases and previous which consist of only few microcysts. The  US showed an oval mass arising from the pancreatic head with multiple small echofree areas lined by echogenic material (Fig. 1). Body and tail of the pancreas showed a normal echogenic patter. The main pancreatic duct and the biliary system were normal without signs of compression or occlusion.
CT of the abdomen obtained 1 week prior to admission showed a large inhomogeneous mass arising from the pancreatic head with a large apical radiolucent area (Fig. 2). ERCP demonstrated multiple cysts of various size communicating with the main pancreatic duct (Fig. 3). The MPD showed a normal morphology. On laparotomy a well demarcated multicystic enlargement of the pancreatic head adjacent to the, duodenum but without signs of invasive  growth was found (Fig. 4). A Traverso procedure (duodenum-preserving pancreatic head resection) was performed.
Specimen radiographs of the excised tumor after cannulation of the MPD showed fine calcifications, within the tumor and a single calcified cystic structure. After injection of contrast material multiple cysts were filled via communications with otherwise normally configured ductal branches (Fig. 5).
The specimen (Fig. 6) was sent for histologic examination. The patient recovered well and  was discharged from hospital 10 days after surgery.

Pathologic Findings
Macroscopically, the ovoid and well circumscribed tumor arising from the pancreatic head measuring 95 x 80 x 50 mm consisted of multiple cysts of various sizes. The tumor surface was smooth, well defined and free of solid nodules (Fig. 5). The pancreatic parenchyma appeared to be of normal consistency and the proximal pancreatic duct was of regular shape.
Microscopically, cross sections of the tumor showed cysts of various size but smaller than 20mm containing an eosinophilic liquid. The cysts were lined by a single layer of glycogen-rich flat or cuboidal cells with small pleomorphic nuclei (Fig. 6). Chromogranin-and Ki67-1abelling indices were 1%. No mucous nor mucinous or myoepithelial cells were found. The cysts appeared to be trapped in a webwork of partially fibrotic pancreatic parenchyma with few islets of normal pancreatic tissue, regular as well as degenerated acinar structures and small intralobular ducts.
Serous cystadenomas usually arise from the head or body of the pancreas and seldom involve the entire organ. Their typical sonographic and radiologic feature is a uniform composition of multiple small (<2 cm) cysts. They show a central fibrous scar and "sunburst" calcifications throughout the tumor stroma and sometimes signs of hypervascularisation 10,11]. On ERCP the MPD is either normal, displaced or compressed by the tumor mass [7]. Their macroscopic aspect is that of an ovoid well defined tumor with a smooth but irregular shape due to their polycystic composition. Frequently there is fibrous sometimes calcified tissue trapped in-between the cysts. Their microscopic pattern is.characterized by the uniform architecture of the cysts lined by flat or cuboidal glycogen-rich epithelium [3]. The ultrastructure of these epithelial cells displays traits of ductal, centroacinar, acinar and islet cell of which the centroacinar cell seems to share the most similarities with the neoplastic epithelium [1].
The common detection of intracytoplasmic glycogen and the occasional finding of myoepithelial cells in SCA [17] has raised the question whether the origin of SCA may be the more proximal ductal cell. In the human pancreas myoepithelium can be found only in the MPD.
,The case of SCA we report above displays most of the common macro-and microscopic characteristics of such tumors, yet it presents another incidence of serous cystadenoma of the pancreas where cysts communicate with the pancreatic duct. The described tumor, however, differs from the lesion seen by Furukawa et al., where a single cyst communicated with the MPD. In our case ERCP demonstrated various cysts in communication with the branches of the MPD in an alveolar-like pattern. It seems to be unlikely that such a pattern of communication is due to erosion of the pancreatic duct by growing cysts as it has been hypothesized by Furukawa [6]. Our findings rather suggest that SCA may arise from ductal epithelium proximal of the centroacinar cell. Positive Chromagranin-staining of cystic epithelium as found in our specimen is indicative of ductal cells [1]. However, we did not find any myoepithelial cells in the tumor that would further support the hypothesis of a ductal origin of these tumors. Careful examination of further cases of serous cystadenoma is needed to further clarify the histogenesis of this rare pathological entity.