Microscopic description and IHC:

Histological sections of the pancreatic cyst demonstrate mucinous-secreting columnar type epithelial lining with focal areas show marked loss of nuclear polarity, marked nuclear atypia and increased mitosis.

The mural nodule within the cyst is composed of ribbons, nests and trabeculae of neoplastic cells with round nuclei and fine stippled chromatin. Additionally, extracellular and intracellular eosinophilic secretions/globules are noted.

Immunostains performed show the neoplastic cells in the mural nodule are positive for AE1/3, synaptophysin, chromogranin; and negative for beta-catenin nuclear staining, chymotrypsin and trypsin. The ki-67 proliferative index labels up to 3.5% of tumor cells.

Discussion:

Intraductal papillary mucinous neoplasm (IPMN) is a unique non-invasive pancreatic neoplasm either arising from main duct or branch duct and is defined by a grossly visible lesion (>1cm). IPMN typically lacks ovarian-type stroma as opposed to mucinous cystic neoplasm. Appropriate classification of IPMN into main duct or branch duct type is important as it reflects differences in clinical management and prognosis. Invasive carcinoma arises in approximately 40% of IPMN cases and therefore, extensive sampling, preferably complete submission, is crucial to rule out this possibility. IPMN can be mutlifocal in 20-40% of cases.

Concomitant presence of pancreatic neuroendocrine tumor (NET) in conjunction with IPMN has been reported in the literature, but it is unclear whether this represents a true association or by chance only.

Several studies showed that concomitant association of IPMN and NET is found to be more frequent than previously expected. In reported cases, the most common degree of dysplasia of IPMN was low-grade but high-grade dysplasia was also noted in few cases. NETs were typically small in size (mean, 1.51 cm). Metastasis of NET may occur in concomitant cases with IPMN even in small sized tumors.

Moreover, metachronous or synchronous extra-pancreatic carcinomas may exist, particularly colorectal and gastric adenocarcinomas. Therefore, careful follow up to screen for extra-pancreatic malignant neoplasms and to detect concomitant NETs may be necessary.

References:

Gill KR, Scimeca D, Stauffer J,Krishna M, Woodward T, Jamil LH, Wallace MB, Nguyen JH, Raimondo M. Pancreatic Neuroendocrine Tumors among Patients with Intraductal Papillary Mucinous Neoplasms: Real Association or Just a Coincidence? JOP. J Pancreas (Online) 2009 Sep 4; 10(5):515-517.

Castellano-Megías VM, Andrés CI, López-Alonso G, Colina-Ruizdelgado F. Pathological features and diagnosis of intraductal papillary mucinous neoplasm of the pancreas. World Journal of Gastrointestinal Oncology. 2014;6(9):311-324.

Ishida M, Shiomi H, Naka S, Tani T, Okabe H. Concomitant intraductal papillary mucinous neoplasm and neuroendocrine tumor of the pancreas. Oncology Letters. 2013;5(1):63-67.

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