Arch Pathol Lab Med—Vol 125, December 2001 Serous Cystadenoma of the Pancreas—Rampy et al 1591 Serous Cystadenoma of the Pancreas With Papillary Features A Diagnostic Pitfall on Fine-Needle Aspiration Biopsy Bill A. Rampy, DO, PhD; Irving Waxman, MD; Shu-Yuan Xiao, MD; Roberto Logron ˜o, MD ● Serous cystadenoma of the pancreas is an uncommon neoplasm that occasionally exhibits papillary differentia- tion. The cytomorphologic structure of pancreatic serous cystadenoma has been rarely described, and, to our knowl- edge, such papillary morphologic structure has never been reported on fine-needle aspiration cytologic examination. We present a case of serous cystadenoma of the pancreas in a 77-year-old woman. Endoscopic ultrasonography showed a well-demarcated solid/cystic mass in the mid- body of the pancreas, suggestive of solid pseudopapillary tumor. Aspiration cytologic examination, performed under endoscopic ultrasound guidance, showed a predominantly papillary epithelial neoplasm consistent with the radiologic impression. Gross and histologic examination of the ex- cised specimen revealed a pancreatic serous cystadenoma with multifocal papillae. This case illustrates the cytomor- phologic structure of serous cystadenoma that presents with prominent papillary differentiation on aspiration cy- tologic examination. The unusual cytologic appearance of this tumor introduces significant diagnostic challenges to the pathologist. Serous cystadenoma must be included in the differential diagnosis of pancreatic neoplasms with papillary morphologic structure as evaluated by fine-nee- dle aspiration cytologic examination. (Arch Pathol Lab Med. 2001;125:1591–1594) S erous cystadenoma (SC), also known as microcystic ad- enoma or glycogen-rich cystadenoma, is a rare, usu- ally benign pancreatic neoplasm that occurs most often in women and is typically diagnosed during the sixth to ninth decades of life. The characteristic histologic features of this tumor include multiple microcysts separated by fine connective tissue septa, lined by flattened or cuboidal epithelium, and most often filled with proteinaceous fluid. Less common presentations of SC include the oligocystic variant with fewer but larger cysts and a predominantly solid form. The cytomorphologic structure of pancreatic Accepted for publication June 4, 2001. From the Departments of Pathology (Drs Rampy, Xiao, and Logron ˜o) and Medicine (Dr Waxman), University of Texas Medical Branch, Gal- veston, Tex. No financial support was provided for this article. Reprints: Roberto Logron ˜o, MD, University of Texas Medical Branch, Cytopathology Division, Department of Pathology, 9.300 John Sealy Annex, 301 University Blvd, Galveston, TX 77555-0548 (e-mail: Rol- ogron@utmb.edu). SC has been described only rarely. 1–7 Whereas intracystic papillary growth of neoplastic epithelium has been his- tologically described for SC, 8 to the best of our knowledge, no such morphologic structure has been previously re- ported in the cytology literature. REPORT OF A CASE A 77-year-old woman presented to the University of Texas Medical Branch at Galveston with mild abdominal pain. Admis- sion history and physical examination depicted a normally active individual with no remarkable weight loss, nausea, emesis, or changes in bowel habits. Medical history, as related by the pa- tient, was significant for the occurrence of a mild stroke several years earlier and a similar episode recently that was associated with resultant aphasia. Evaluative procedures administered with regard to this more recent event included ultrasonography and computed tomographic (CT) exploration of the head and carotid arteries and a CT survey of the chest and abdomen. Available medical records do not address the results of the head and neck studies; abdominal CT, however, revealed a 5.2  4.5  4-cm mass within the midbody of the pancreas without evidence of biliary dilatation or metastases. A follow-up esophagogastroduo- denoscopy with endoscopic ultrasound (EUS) was performed and demonstrated the lesion to be a well-defined, solid/cystic pancreatic mass that displaced the celiac axis without invasion and was thought to be suggestive of solid pseudopapillary tumor. Fine-needle aspiration (FNA) cytologic examination was per- formed with endoscopic image guidance. An exploratory lapa- rotomy with distal pancreatectomy was subsequently performed. EUS Findings A 4.0  3.8-cm mass in the region of the pancreatic body was noted, displacing, but not invading, the celiac trunk. The lesion was round and had well-defined margins. The ultrasonic image displayed solid and cystic components (Figure 1). Atrophy was noted throughout the pancreas, and the gallbladder was normal. No lymph nodes were visualized. The FNA was performed under ultrasonographic guidance. The ultrasonographic findings were consistent with a pancreatic cystic neoplasm, and the differential diagnosis included solid pseudopapillary neoplasm and non- functioning islet cell tumor. Cytologic Findings The aspirates were expressed onto glass slides and smears were prepared. A total of 3 smears (1 from each needle pass) were air-dried and immediately stained with Quik-Dip (Merce- des Medical Inc, Sarasota, Fla) for rapid assessment of specimen adequacy and preliminary evaluation at the endoscopy suite. Ad- ditionally, 13 smears were immersed in 95% ethanol for fixation and further Papanicolaou staining. The needles were rinsed in