Microscopic description and IHC:

The pancreas is totally submitted for evaluation. Grossly, The entire pancreatic main and branch ducts are dilated (most prominent at pancreatic head). There are numerous irregular, shaggy, pink tumors dispersed throughout the pancreatic head, predominantly within the pancreatic duct system. Microscopic examination shows the tumors are intraductal neoplasm with extensive high-grade dysplasia with frequent necrotic foci. The neoplasm is composed of cuboidal to columnar cells, arranged in complex tubulopapillary structures. No visible mucin is identified. The entire background pancreas demonstrates chronic atrophic pancreatitis with no residual normal pancreatic parenchyma.

The neoplastic cells are negative for synaptophysin and negative for acinar cell differentiation (trypsin, and chymotrypsin). A beta-catenin stain is negative for abnormal nuclear expression.

Discussion:

According to WHO 2010 classification, pancreatic intraductal neoplasms include Intraductal Papillary Mucinous Neoplasm (IPMN) and Intraductal Tubulopapillary Neoplasms (ITPN). The oncocytic variant of IPMN is also termed intraductal oncocytic papillary neoplasm (IOPN) by some authorities, due to its differing molecular characteristics and better prognosis than conventional IPMN.

ITPN is rare, accounting for <1% of all pancreatic exocrine neoplasms and only 3% of intraductal neoplasms of the pancreas. Patients with ITPN are typically a decade younger than patients with IPMN. In a case series report by Yamaguchi et al, 5 men and 5 women with a mean age of 58 years presented with this lesion. About half of ITPNs occur in the head of pancreas; a third diffusely involved the gland, and 15% are localized to the tail.

The characteristic features of ITPN are ; (1) the appearance of a solid nodular tumor obstructing dilated ducts on macroscopic examination; (2) no visible secreted mucin; (3) tubulopapillary growth; (4) uniform high-grade atypia throughout the neoplasm; (5) easily recognizable necrotic foci; (6) ductal differentiation, as indicated by CK7 and/or CK19 expression; (7) absence of acinar differentiation, as indicated by the absence of trypsin; (8) absence of MUC2, MUC5AC, and fascin; and (9) absence of mutations in KRAS and BRAF.

The prognosis of ITPN remains to be investigated; they appear to have better prognosis than IPMN.

Table depicting ITPN features
References:

Yamaguchi, Hiroshi, et al. (2009) "Intraductal tubulopapillary neoplasms of the pancreas distinct from pancreatic intraepithelial neoplasia and intraductal papillary mucinous neoplasms." The American journal of surgical pathology 33, 1164-1172.

Date, K., Okabayashi, et al. (2016). Clinicopathological features and surgical outcomes of intraductal tubulopapillary neoplasm of the pancreas: a systematic review. Langenbecks Arch Surg 401, 439-447.

Rooney, S.L., and Shi, J. (2016). Intraductal Tubulopapillary Neoplasm of the Pancreas: An Update From a Pathologist's Perspective. Arch Pathol Lab Med 140, 1068-1073.

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