The string sign for diagnosis of mucinous pancreatic cysts.
OBJECTIVE
Pancreas cyst fluid analysis does not provide optimal discrimination between mucinous and nonmucinous cysts. The aim of this study was to assess the performance characteristics of the "string sign" - a test performed at the time of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA), for the diagnosis of mucinous pancreatic cysts (branch duct intraductal papillary mucinous neoplasms [bIPMN] and mucinous cystic neoplasms).


METHODS
Patients undergoing EUS-FNA of pancreatic cystic lesions at one referral center between 2003 and 2012 were included. The string sign was performed prospectively, and was considered positive if ≥ 1 cm string formed in cyst fluid and lasted for ≥ 1 second. Performance characteristics of the string sign and a sequential cyst fluid test interpretation model were assessed.


RESULTS
For 98 histologically proven cases, the sensitivity, specificity, positive predictive value, and negative predictive value of the string sign for diagnosis of mucinous cysts were 58 % (95 % confidence interval [CI] 44 % - 70 %), 95 % (83 % - 99 %), 94 % (81 % - 99 %), and 60 % (46 % - 72 %), respectively. When string sign results and carcinoembryonic antigen (CEA) concentration (≥ 200 ng/mL) were combined, diagnostic accuracy improved from 74 % and 83 %, respectively, to 89 % (P ≤ 0.03). Among bIPMN, a positive string sign was associated with gastric and intestinal epithelial subtypes. The sequential cyst fluid test interpretation model (including cytology, mucin stain, CEA, and string sign) yielded an overall sensitivity for mucinous lesions of 96 %, with a specificity of 90 %.


CONCLUSIONS
The string sign is highly specific for diagnosis of mucinous pancreatic cysts, and improves overall diagnostic accuracy of pancreatic cyst fluid analysis. Sequential cyst fluid test interpretation yields high diagnostic sensitivity and specificity for mucinous cysts.
Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota, United States.
Benjamin L
BL
Bick
Department of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, Minnesota, United States.
Felicity T
FT
Enders
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Michael J
MJ
Levy
Department of Anatomic Pathology, Mayo Clinic, Rochester, Minnesota, United States.
Lizhi
L
Zhang
Department of Anatomic Pathology, Mayo Clinic, Rochester, Minnesota, United States.
Michael R
MR
Henry
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Barham K
BK
Abu Dayyeh
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Suresh T
ST
Chari
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Jonathan E
JE
Clain
Department of Gastroenterologic and General Surgery, Mayo Clinic, Rochester, Minnesota, United States.
Michael B
MB
Farnell
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Ferga C
FC
Gleeson
Department of Gastroenterologic and General Surgery, Mayo Clinic, Rochester, Minnesota, United States.
Michael L
ML
Kendrick
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Randall K
RK
Pearson
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Bret T
BT
Petersen
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Elizabeth
E
Rajan
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Santhi Swaroop
SS
Vege
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, United States.
Mark
M
Topazian
D020420:Cyst Fluid; D003937:Diagnosis, Differential; D061765:Endoscopic Ultrasound-Guided Fine Needle Aspiration; D006801:Humans; D009093:Mucus; D010181:Pancreatic Cyst / Q000000981:diagnostic imaging / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity