Intraductal papillary neoplasm of the bile duct, gastric type, arising in the intrapancreatic common bile duct could progress to colloid carcinoma: report of a case

Abstract

Intraductal papillary neoplasm of the bile duct (IPNB) exists in a pathway of multistep-carcinogenesis toward cholangiocarcinoma. Four subtypes are observed in IPNB, pancreatobiliary type, intestinal type, gastric type, and oncocytic type, similarly to the corresponding disease in the pancreas, intraductal papillary mucinous neoplasm (IPMN). IPNB can present with or without macroscopically visible mucin secretion. IPNB usually progresses to tubular adenocarcinoma. However, there are a limited number of well-described cases of gastric-type IPNB progressing not to tubular adenocarcinoma but to colloid carcinoma. Herein, we present a case of an 82-year-old female patient with gastric-type IPNB in the intrapancreatic common bile duct without macroscopically visible mucin secretion, which progressed to colloid carcinoma. As IPNB, especially without visible mucin secretion, is considered to be a heterogeneous group of diseases, such an unexpected association could occur.

Keywords: Intraductal papillary neoplasm of the bile duct; colloid carcinoma; gastric type; intraductal papillary mucinous neoplasm.

Figure 1

Computed tomography (A-C) and magnetic resonance imaging (D, E) findings. (A) The tumor (arrow) was located in the intrapancreatic common bile duct, measuring 20 × 18 mm. (B, C) The peripheral portion of the tumor (arrow) was predominantly contrast-enhanced on the arterial phase (C) compared with the plain computed tomography image (B). (D) The tumor (arrow) showed low-signal intensity on a T1-weighted image. (E) The tumor (arrow) showed high-signal intensity on a T2-weighted image.

Figure 2

Macroscopic findings. A. The tumor, measuring 22 × 20 × 18 mm, was located in the intrapancreatic common bile duct. B. On the cut surface, the tumor showed a mucinous appearance and infiltrated the wall of the bile duct with pushing borders.

Figure 3

Microscopic findings. (A) The tumor was composed of intraductal and invasive components. The intraductal component showed papillary growth with fibrovascular cores; the invasive component revealed abundant extracellular mucin (× 20). (B) Higher magnification of the boxed area in (A). The invasive component and the intraductal component showed gradual transition with an intervening area of mucin-hypersecreting dilated glands (× 100). (C) The intraductal component consisted of tumor cells containing abundant mucin in the cytoplasm and mildly enlarged nuclei with indistinct nucleoli (× 400). (D) The invasive component was composed of tumor cells present in the periphery of the mucinous lake or floating in the mucinous lake; their nuclei were moderately enlarged with prominent nucleoli (× 400).

Figure 4

Immunohistochemical findings. A. Almost all the tumor cells were positive for CK7 (× 100). B. Only the invasive component was weakly positive for CK20 (× 100). C. All tumor cells were negative for CDX2 (× 100). D. MUC1 immunostaining was observed in secreted mucin but not in tumor cells (× 100). E. MUC2 immunostaining was observed only focally in the intraductal component and diffusely in the invasive component (× 100). F. Patchy MUC5AC positivity was observed in the intraductal component and diffuse MUC5AC positivity was noted in the invasive component (× 100). G. Almost all the tumor cells were positive for MUC6 (× 100). H. The Ki-67 labeling index was 4.6% in the intraductal component and 32% in the invasive component (× 100). I. Diffuse nuclear accumulation of p53 was observed in both components (× 100).