Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012 33

Case Report O G H Re p o r t s

A unique case of gallbladder cancer arising in the neck side of segmental adenomyomatosis that mimicked hepatocellular carcinoma on contrast CTKeita Kai,1 Takao Ide,2 Ryoko Egashira,3 Yasuo Koga,2 Kota Wakiyama,2 Kenji Kitahara,2 Hiroyuki Irie,3 Hirokazu Noshiro,2 Osamu Tokunaga1

1Department of Pathology & Microbiology, Saga University Faculty of Medicine, Saga, Japan2Department of Surgery, Saga University Faculty of Medicine, Saga, Japan3Department of Radiology, Saga University Faculty of Medicine, Saga, Japan

INTRODUCTION

Adenomyomatosis (ADM) of the gallbladder is defined as an epithelial proliferation and hypertrophy of the mus-cularis with outpouching of the mucosa into or through the thickened muscular layer, forming the so-called Rokitansky–Aschoff sinuses (RAS). Adenomyomatosis is categorized by its gross features as the diffuse type, fundal (localized) type or segmental type.[1 –3] The segmental type

of ADM forms an annular stricture comprising a thickened wall dividing the gallbladder lumen into separate intercon-nected compartments, with or without diffuse wall thick-ening on the fundal side. Several reports have described that gallbladder cancer was sometimes found in the fundal side of the segmental type of ADM.[3,4,5] but cancer aris-ing on the neck side of the segmental type of ADM is extremely rare. We recently encountered a unique case of gallbladder cancer arising in the neck side of segmental ADM. Further, this case showed unusual morphology and mimicked hepatocellular carcinoma in an imaging study.

CLINICAL SUMMARY

A 53-year-old Japanese female suffered from right hypo-chondrial pain and was admitted to a local hospital under

*Corresponding address: Keita Kai Department of Pathology & Microbiology,Faculty of Medicine, Saga University Nabesima 5-1-1,Saga City, Saga 849-8501, JapanTel: +81-952-34-2234; Fax: +81-952-34-2055Email: kaikeit@cc.saga-u.ac.jp

DOI: 10.5530/ogh.2012.1.7

ABSTRACT

A 53-year-old Japanese female was admitted to our hospital for examination and treatment of an abdominal mass lesion. Contrast-enhanced abdominal computed tomography (CT) showed a well-circumscribed mass that measured approximately 5 cm. Although the tumor was located near the neck of the gallbladder, it seemed to be pedunculated from the liver parenchyma. From the enhancement pattern and morphological characteristics of the contrast CT images, the nodule was preoperatively diagnosed as hepatocellular carcinoma. The patient underwent a laparotomy, and it was intraoperatively revealed that the tumor existed solely in the neck of the gallbladder without serosal invasion. Whole-layer cholecystectomy with lymph node dissection was therefore performed. A pathological examination revealed that the papillary tumor filled up the neck side lumen of the segmental type of adenomyomatosis (ADM). The tumor was histologically diagnosed as papillary adenocarcinoma. Cases of papillary adenocarcinoma arising on the neck side lumen of the segmental type of ADM are extremely rare. Furthermore, no such case of gallbladder cancer which mimicked hepatocellular carcinoma has previously been reported.

Keywords: Gallbladder cancer, adenomyomatosis, papillary adenocarcinoma, hepatocellular carcinoma.

Keita Kai, et al.: A unique case of gallbladder cancer arising in the neck side of segmental adenomyomatosis

34 Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012

the diagnosis of acute cholecystitis. She underwent treatment for acute cholecystitis, and the presence of gallstones and an abdominal mass lesion were found by an imaging study. The patient was subsequently admitted to our hospital for further examination and treatment of the abdominal mass lesion. Laboratory tests performed on admission revealed no abnormality in the patient’s red blood cell count (4.78 ×106/μl), hemoglobin concentra-tion (12.2 g/dl), white blood cell counts (7600/μl) or platelet count (28.1 ×104 /μl). Serology and coagulation tests also showed no abnormalities. All of the examined tumor markers were within normal ranges, including those for carcinoembryonic antigen (CEA), carbohydrate antigen (CA)19-9, Dupan-2 antigen, SPan-1 antigen, protein induced by vitamin K absence (PIVKA)-II and alpha-fetoprotein (AFP).

Contrast-enhanced abdominal computed tomography (CT) showed a well-circumscribed mass that measured approximately 5 cm. The tumor showed mild enhance-ment in the early phase, and this enhancement was washed out in delayed phase (Fig. 1). Although the tumor was located near the neck of the gallbladder, it seemed to be pedunculated from the liver parenchyma of seg-ment 6 (Fig. 2). The structures of the neck of the gall-bladder and the cystic duct were unclear in the images. After discussion of whether the tumor originated from the liver parenchyma or the neck of the gallbladder, a preoperative diagnosis of hepatocellular carcinoma at segment 6 of the liver was made. Under the presumed diagnosis of hepatocellular carcinoma, surgical resection

was performed. Intraoperatively, the tumor was found to be located at the neck of the gallbladder, and no sero-sal invasion or adhesion to other organs was observed. Whole-layer cholecystectomy was performed. The his-tology of the papillary adenocarcinoma and the surgical margin of the cystic duct were intraoperatively con-firmed by a frozen section analysis. After the histological examination of frozen sections, lymph node dissection was additionally performed, and the operation was com-pleted. The patient’s postoperative course was unevent-ful, and she was discharged from the hospital two weeks after the operation.

PATHOLOGICAL FINDINGS

A grossly papillary tumor filled up the neck side lumen of the segmental type of ADM (Fig. 3). The fundal side lumen contained white gall and a lot of gallstones. His-tologically, atypical tumor cells proliferated as tubular structures in part, but dominantly showed a papillary structure, and were therefore diagnosed as papillary adenocarcinoma (Fig. 4a). The tumor invaded into the subserosal layer, but no serosal invasion was observed. A lot of dilated RAS were observed at the annular stric-ture (Fig. 4b). No cancer metastasis was observed in the examined lymph nodes.

DISCUSSION

Adenomyomatosis of the gallbladder has not been considered to have malignant potential. However, there

Figure 1. a) The early phase of the contrast abdominal CT. A well-circumscribed mass (arrow) showed heterogeneous enhancement by contrast medium. b) The delayed phase of the contrast abdominal CT. The enhancement of the nodule was washed out in this phase (arrow).

Figure 2. The sagittal view of the contrast abdominal CT. Although the tumor was located near the neck of the gallblad-der, it seemed to be pedunculated from the liver parenchyma (arrow).

(a) (b)

Keita Kai, et al.: A unique case of gallbladder cancer arising in the neck side of segmental adenomyomatosis

Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012 35

have been several reports suggesting that gallblad-der cancer may originate from adenomyomatosis[6–10] or indicating that patients with the segmental type of adenomyomatosis have an increased risk of develop-ing gallbladder cancer.[3,4] Most of these reported cases were of gallbladder cancer that arose on the fundal side of the segmental type of ADM. We have previ-ously analyzed 97 cases of surgically resected gallblad-der cancer and reported that 25 (25.8%) out of 97 cases were grossly accompanied with ADM.[5] In our previous series, there were only two cases where the gallbladder cancer had arisen on the neck side of the segmental type of ADM. Furthermore, no papillary

adenocarcinoma was noted in our previous series of gallbladder cancer with ADM. Therefore, the present case where the papillary adenocarcinoma has arisen on the neck side of the segmental type of ADM is consid-ered to be extremely rare.

Another interesting feature of present case is that the tumor mimicked hepatocellular carcinoma in the con-trast CT images. Usually, it is easy to distinguish gallblad-der cancer from hepatocellular carcinoma during imaging studies. We believe that there were several characteris-tics of the tumor and accidental factors that led to the unusual appearance of the nodule. First, the tumor filled up the cavity of the neck side of the segmental type of ADM and was demonstrated as a solid tumor in the CT images. Second, the lumen of the fundal side was mark-edly dilated, and made it look as if the lumen was the entire lumen of the gallbladder. Third, the tumor existed very close to the liver parenchyma, and it looked as if the tumor was pedunculated from the liver parenchyma. Fourth, the enhancement pattern of the contrast CT images was consistent with the pattern of HCC rather than gallbladder cancer. The usual enhancement pattern of invasive gallbladder cancer is a gradual enhancement reflecting the stromal component of the tumor. Usu-ally, papillary adenocarcinoma contains a small amount of stroma, and the stroma of papillary adenocarcinoma contains a lot of blood vessels compared to other his-tological types of adenocarcinoma. These histological characteristics probably led to the early enhancement on contrast CT.

In summary, we have herein presented a unique case of gallbladder cancer arising in the neck side of a segmen-tal adenomyomatosis that mimicked hepatocellular carci-noma on contrast CT. Although this is a very rare case, and was modified by several unusual conditions, we have reported this case as a reference for similar cases that might be encountered in the future.

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Figure 3. The gross appearance of the resected gallbladder. The papillary tumor filled up the neck side lumen of the seg-mental type of adenomyomatosis.

Figure 4. The histopathological features. a) The papillary adenocarcinoma (hematoxylin and eosin, × 100). b) A lot of dilated Rokitansky–Aschoff sinuses were observed at the an-nular stricture of the resected gallbladder (hematoxylin and eosin, × 40).

(a) (b)

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36 Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012

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