Introduction
The diagnosis of mucinous cysts including intraductal papillary mucinous neoplasm (IPMN) and mucinous cystic neoplasm (MCN) by cytology can significantly impact patient management; however, the diagnosis can be challenging, especially when there is scant material. We aim to describe the cytomorphologic characteristics and the influence of the cytologic findings on clinical management.

Materials and Methods
We identified patients who underwent endoscopic ultrasound and were found to have cysts containing mucin based on cytology. The EUS features, gross aspirate characteristics, ancillary chemistry tests, and cytomorphology were described.

Results
Fourteen patients, who underwent endoscopic ultrasound-guided fine-needle aspiration of pancreatic cysts, had mucin identified by cytology. Four cysts had scant mucin; five were moderate, and five were abundant (Table 1). The texture of the mucin varied from granular to colloid-like with features including cracking, ferning, and folding. Seven aspirates contained glandular cells that ranged from mildly to moderately atypical. Seven aspirates had concurrent CEA, amylase, and lipase samples. Three cases had CEA less than 192ng/ml, and four cases had CEA greater than 192ng/ml. Most cases had significantly elevated amylase and lipase. In thirteen cases out of fourteen, the clinical assessment following cytologic diagnosis was either IPMN or MCN. In five cases, cytologic findings changed the clinical impression from pancreatic cyst not otherwise specified to IPMN or MCN. In six cases, the clinical impression of IPMN was supported. In one case, the clinical impression of pseudocyst was changed to IPMN. In one case, the clinical impression of pancreatic cyst NOS was assessed as pseudocyst after fine-needle aspiration.

The chemical analysis of cyst fluid has been investigated in several studies. The chemical analysis included amylase levels, lipase levels, carcinoembryonic antigen (CEA) levels, and others [3,7,8,9]. High levels of some markers like CEA (cut off of 192 ng/ml) suggested more of a mucinous producing tumor whereas elevated enzymes such as amylase, and lipase favored more of an inflammatory process. Mucin has been found in a variety of pancreatic cysts, although it is most commonly found in mucinous cystic neoplasms (MCNs) and intraductal papillary mucinous neoplasms (IPMNs) [10,11,12,13].

Cyst's mucin content has also been studied in several studies. The features of mucin, including the amount of mucin, the texture of the mucin, the color of the mucin, and the presence of benign or atypical glandular components, can aid in the diagnosis. Where high levels of viscous and cellular material suggested more of a mucinous producing neoplasm[13,14,15,16,17].

In all of our fourteen cases, the morphology of the mucin helped us further exclude inflammatory cysts, suggested true cystic lesions in some cases, and raised the suspicion of possible dysplastic processes in rare cases.

Conclusion
Fine needle aspirate can be useful in determining the nature of a pancreatic cyst. Although the aspirate may yield scant material and cellularity, the cytomorphologic features, when considered with radiographic, and chemical findings, can help determine if the cysts are neoplastic. Although some aspirates in the case series were acellular and CEA levels less than 192ng/ml, the presence of mucin raises the concern for mucinous neoplasm, warranting surveillance by endoscopic ultrasound. This case series highlights the importance of detecting and reporting the presence of mucin by cytology.