The differential diagnosis of cysts of the pancreas includes inflammatory (pseudocysts), benign (serous), premalignant (mucinous), and malignant (mucinous) lesions. The purpose of this study was to determine the most accurate test for differentiating mucinous from nonmucinous cystic lesions. The results of EUS imaging, cyst fluid cytology, and cyst fluid tumor markers (CEA, CA 72-4, CA 125, CA 19-9, and CA 15-3) were prospectively collected and compared in a multicenter study using histology as the gold standard.   One hundred twelve of these patients underwent surgical resection, providing a histologic diagnosis of the cystic lesion (68 mucinous, 7 serous, 27 inflammatory, 5 endocrine, and 5 other). Receiver operator curve analysis of the tumor markers demonstrated that cyst fluid CEA (optimal cutoff of 192 ng/mL) demonstrated the greatest area under the curve (0.79) for differentiating mucinous vs. nonmucinous cystic lesions. The accuracy of CEA (88 of 111, 79%) was significantly greater than the accuracy of EUS morphology (57 of 112, 51%) or cytology (64 of 109, 59%) (P < 0.05). There was no combination of tests that provided greater accuracy than CEA alone (P < 0.0001).  

The differentiation of cystic pancreatic tumors preoperatively can be difficult. Although morphology by EUS may help, there appears to be overlap between non-neoplastic and neoplastic cysts as well as differentiation between neoplastic cysts. EUS guided FNA with cytology analysis is ideal but its accuracy may vary from center to center. Multiple tumor markers in the cyst fluid are being studied for differentiation between cystic pancreatic tumors but which tumor marker is the best and what is the cut-off to be used has been unclear so far. The above study was a multi-center study on cystic pancreatic tumors with histology as the gold standard. The accuracy of cytology in this study of 59% is lower than a recent report from another group. However, this study shows that if one chooses to use tumor markers in cyst fluid for differentiation of pancreatic cystic tumors then the marker of choice should be CEA with a cut-off of 192 ng/ml. This should allow at least 79% accuracy for differentiating mucinous from non-mucinous cystic lesions of the pancreas.

Computed tomography (CT) is the most common method of staging lung cancer. Endoscopic ultrasound guided fine-needle aspiration (EUS-FNA) has been shown to be highly accurate in staging patients with nonsmall cell lung cancer (NSCLC) who have enlarged mediastinal lymph nodes on CT scan. In this study the authors report the accuracy and yield of EUS-FNA in staging patients without enlarged mediastinal lymph nodes by CT. Patients with NSCLC and CT scan showing no enlarged mediastinal lymph nodes underwent EUS. EUS guided FNA   was performed if an enlarged lymph node was found by EUS in the upper mediastinum, aortopulmonary window, subcarinal, and periesophagus regions.   Sixty-nine patients without enlarged mediastinal lymph nodes were evaluated. Endoscopic ultrasound detected malignant mediastinal lymph nodes in 14 of 69 patients. In 3 others other evidence of advanced disease was found (1 left adrenal, and 2 with mediastinal invasion of tumor) for a total of 17 of 69 (25%, 95% confidence interval: 16% to 34%) patients. Eleven additional patients were found to have advanced disease by bronchoscopy (2), mediastinoscopy (2), and thoracotomy with mediastinal lymph node dissection (7). The sensitivity of EUS for advanced mediastinal disease was 61% (49% to 75%), and the specificity was 98% (95% to 100%).   The authors concluded that endoscopic ultrasound guided fine needle aspiration can detect advanced mediastinal disease and avoid unnecessary surgical exploration in almost one of four patients who have no evidence of mediastinal disease on CT scan.   This study suggests that all potentially operable patients with nonmetastatic NSCLC may benefit from EUS staging.

The purpose of this study was to identify possible associated factors that may have contributed to failure to detect a pancreatic neoplasm during endoscopic ultrasound (EUS) examinations by experienced endosonographers.   A multicenter retrospective study was organized, and 20 cases of pancreatic neoplasms missed by nine experienced endosonographers were identified. Careful analysis of each case was carried out to identify the factors that might have led to the missed diagnosis on EUS. Twelve patients with a missed pancreatic neoplasm had EUS features of chronic pancreatitis. Other factors that might have increased the likelihood of a false-negative EUS examination included a diffusely infiltrating carcinoma (n = 3), a prominent ventral/dorsal split (n = 2), and a recent episode (within the previous 4 weeks) of acute pancreatitis (n = 1). Five patients with a negative initial EUS underwent a follow-up EUS after 2-3 months, with a pancreatic mass being found in all cases. Three patients had a diffusely infiltrating pancreatic adenocarcinoma. The authors concluded that EUS is not a foolproof method of detecting a pancreatic neoplasm. Possible associated factors that may increase the likelihood of a false-negative EUS examination include chronic pancreatitis, a diffusely infiltrating carcinoma, a prominent ventral/dorsal split and a recent episode (< 4 weeks) of acute pancreatitis. If there is a high clinical suspicion of pancreatic neoplasm, if EUS and other imaging methods are negative, and if the patient does not undergo surgery, this study suggests that a repeat EUS after 2-3 months may be useful for detecting an occult pancreatic neoplasm.

This study is a retrospective case series and is an effort to identify associated factors and possible reasons for missing a pancreatic neoplasm on EUS. Although EUS is highly accurate for detection of a pancreatic neoplasm, this study suggests that EUS like other imaging modalities is not fool proof. Associated factors that may have contributed to experienced endosonographers missing a pancreatic neoplasm are outlined in the study. The study is not perfect and has flaws primary due to its retrospective nature and inability to comment on the true frequency of EUS missing a pancreatic neoplasm. However, this study suggests that if the clinical suspicion for a pancreatic neoplasm is high, a negative EUS should not be considered as a 100% proof that a pancreatic neoplasm does not exist.