The Spare Fishing Sign, Differentiating Mucin from Mural Nodules in Pancreatic Cysts, Primary Author Shifa Umar, Secondary Author Vinay Chandrasekhar Author Disclosures Mural nodules are predictors of malignancy in mucous-producing cystic neoplasms of the pancreas. The presence of a mural nodule is a consensus criterion for resection of these cysts. Inspected mucin can be confused for mural nodules, however, these are not high-risk findings and do not warrant additional interventions. Therefore, it is critical to be able to differentiate mucin from mural nodules. Prior study at our institute demonstrated CT has a 24% sensitivity and a 100% specificity for detecting mural nodules, while EUS detected mural nodules with 75% sensitivity and 83% specificity. Mucus was often diagnosed by using change in body position and fine needle aspiration. Inter-observer analysis identified three features that distinguished mucus from mural nodules, namely echogenicity of the lesion, edge of the lesion, and presence of a hyperaquicrim. A 43-year-old female with past medical history of right-sided breast cancer, status post-lumpectomy, and radiation on hormonal therapy was referred to pancreas clinic for evaluation of a pancreatic head, slash, unscented cyst. CT demonstrated a cystic lesion in the pancreatic head, measuring approximately 33 by 28 by 41 millimeter. No enhancing mural nodularity or convincing soft tissue components were reported. MRI reported slightly lobulated pancreatic cystic mass in the head, slash, unscented process with a 9-millimeter non-enhancing cystic nodule. EUS was performed. An anechoic lesion suggestive of a cyst was identified in the unscented process of the pancreas with thin septation. There was no obvious communication with the pancreatic duct. An intracystic nodule was identified with a smooth hyperaquic outer rim and a central hypoaquic part favoring a mucin ball. The cyst was measured to be 41.4 by 26 millimeter, with intracystic nodule measuring 7.5 by 11.4 millimeter. The FNA needle is introduced into the cyst. Initially, the lesion could not be selectively targeted, so fluid was first aspirated to partially collapse the cyst. The lesion was then in a favorable location for sampling. The FNA needle was used to puncture the intracystic nodule. The nodule is detached from the cyst wall and mobile. This is described as the spear phishing sign. FNA cytology was consistent with elevated MLAs of 69,410 and modestly elevated CEA of 47, with a cytology negative for malignancy. General impression was patient has a branch duct IPMN with one worrisome feature, and the intracystic lesion was identified to be inspicated mucin, not a mural nodule. Given the presence of only one worrisome feature, a multidisciplinary evaluation decision was made to observe the patient with surveillance MRCP in six months. Mural nodules are often too small to be seen on cross-sectional imaging. Distinguishing a mural nodule on EUS with mucin is challenging. It is important to differentiate intramural nodules versus mucin, as subsequent management includes surgical resection with potentially serious implications. FNAs performed maneuvers such as dislodging or moving an echogenic lesion can help differentiate mucin with mural nodule. Preliminary examination of an intracystic lesion, presence of hyperechoic rim, and evaluating the echogenicity and edge of the lesion is helpful, but there is high interobserver variability. The spare fishing sign is easier to identify and interpret, and may help endoscopists to better identify mucin balls masquerading as mural nodules.

Spare Fishing Sign

Differentiating Mucin

Mural Nodules

Pancreatic Cysts

CT and EUS