Pancreatic Cysts 3 cm or Smaller: How Aggressive Should Treatment Be?

PURPOSE: To retrospectively determine the frequency of malignancy in small (< or =3 cm) pancreatic cysts, to evaluate whether cyst morphologic features can help predict the presence of malignancy, and to determine the natural history of small pancreatic cysts at follow-up imaging. MATERIALS AND METHODS: Institutional review board approval was obtained; informed patient consent was not required. By means of a computerized search, 510 patients with pancreatic cysts that had been detected at computed tomography (CT) or magnetic resonance (MR) imaging were identified. Cysts that were 3 cm or smaller at surgery or endoscopic ultrasonography (US)-guided cyst fluid aspiration and biopsy were included. Eighty-six patients-31 men and 55 women aged 24-89 years-fulfilled the criteria. Patients underwent surgery or were monitored with endoscopic US-guided cyst fluid analysis, cytologic analysis, and follow-up imaging. Imaging findings were compared with surgical and pathology records and with endoscopic US features. Positive predictive values (PPVs) for benignity and malignancy were calculated on the basis of cyst size and absence or presence of septa in the cysts. RESULTS: Forty-eight patients underwent surgery, and 38 were treated nonsurgically. Seventy-five patients had benign cysts; eight, borderline (malignant) neoplasms; and three, carcinoma in situ lesions. The PPV of small pancreatic cysts for prediction of benignity was 87% (75 of 86 patients). Thirty-six patients had unilocular cysts (35 with benign lesions, one with borderline neoplasm). The PPV of unilocular cysts for prediction of benignity was 97% (35 of 36 patients). Fifty patients had septated cysts; seven of these patients had borderline neoplasms, and three had carcinoma in situ lesions. For prediction of malignancy in small cysts, the PPV of septa was 20% (10 of 50 patients), which was significantly higher than the 3% (one of 36 patients) PPV of unilocular cysts (P = .042). No significant changes in cyst morphologic features were seen in patients who were followed up with imaging for a mean period of 21.8 months. CONCLUSION: The majority (n = 75) of small pancreatic cysts were benign. Thirty-six cysts were unilocular, and virtually all of these (n = 35) were benign. The presence of septa was associated with borderline or in situ malignancy in 20% (10 of 50) of cases.