Case Report: A Unique Pancreatic Tumor with Exclusive Hepatocytic Differentiation

Transcription

1 Available online at Annals of Clinical & Laboratory Science, vol 36, no. 2, 2006 Case Report: A Unique Pancreatic Tumor with Exclusive Hepatocytic Differentiation Natalie NC Shih, 1 Jeffrey SH Tsung, 1 An-Hang Yang, 2 Mei-Hua Tsou, 1 and Tsung-Yen Cheng 3 1 Department of Pathology and Laboratory Medicine, 3 Department of Surgery, Koo Foundation, Sun Yat- Sen Cancer Center, Taipei, and 2 Department of Pathology, Veteran General Hospital, Taipei, Taiwan. Abstract. Only 7 cases of pancreatic tumor with hepatocytic differentiation have been reported in the literature, including 6 cases of hepatoid carcinoma and one case of hepatoid adenoma. Diagnosis of hepatoid carcinoma depends on recognition of characteristic histological features, supported by other evidence linked to hepatic lineage including alpha-fetoprotein production, positive immunoreactivity to liver synthesized proteins, and in situ hybridization detection of albumin mrna. In addition, a synchronous focus of carcinoma arising in pancreatic ducts, islet cells, or acinar cells is essential. We report a unique case of pancreatic tumor with exclusive hepatocytic differentiation. In this tumor, we were unable to find a synchronous focus of carcinoma arising in pancreatic ducts, islet cells, or acinar cells, ruling out the possibility of its being hepatoid carcinoma. Long term follow-up can help to determine whether this tumor is benign or malignant. The patterns of reticulin staining and immunohistochemical staining are suggestive of malignancy, but mitotic activity is low and nuclear pleomorphism is minimal. Keywords: pancreatic neoplasm, hepatoid differentiation, carcinoma, immunohistochemistry Introduction Pancreatic tumors with hepatocytic differentiation are very rare. Only 7 such cases have been reported in the literature [1-5], and all except one [6] were associated with malignant behavior and were classified as hepatoid carcinoma. We present a unique case of a pancreatic tumor with exclusive hepatic differentiation. We are unable to determine the nature of this tumor, benign or malignant. Case Report Address correspondence to Jeffrey SH Tsung, M.D., Sun Yat- Sen Cancer Center, No. 125, Lie-Der Road, Peitou District, Taipei, Taiwan, R.O.C; tel ext 1408; fax ; tsung@mail.kfcc.org.tw. An abdominal mass was incidentally discovered by abdominal ultrasonography in a 32-yr-old man during a routine employee health screening examination. The patient had felt fit and healthy. Apart from a vague 10-yr history of intermittent epigastric pain, he had no other systemic symptoms. On admission to the hospital, his physical examination was unremarkable. Laboratory tests including complete blood count, biochemistry profile, and serological tests for hepatitis B and C virus were all within normal limits. Serum levels of alpha-fetoprotein, carcinoembryonic antigen (CEA), and CA19-9 were also within normal limits. Computed tomography revealed an encapsulated mass, about 7 cm in diameter, in the left upper abdomen between the stomach, spleen, and pancreatic tail (Fig. 1). There were no significantly enlarged lymph nodes in the upper abdomen. Most important, there was no focal lesion in the liver. Angiography showed that this hypervascular mass was supplied by pancreatic arteries that originated from the splenic artery. There was no /06/ $1.50, 2006 by the Association of Clinical Scientists, Inc.

2 Hepatocellular pancreatic tumor 217 Fig. 1. An encapsulated mass in the left upper abdomen between the stomach, spleen, and pancreatic tail. Fig. 2. A well-circumscribed green-colored tumor in the pancreas. evidence of a hypervascular tumor in the liver or any other radiologically abnormal findings. Chest X ray was unremarkable. A pre-operative core biopsy of the mass was done and reported as hepatocellular carcinoma. The patient underwent distal pancreatectomy and splenectomy. The patient is alive and well, without evidence of recurrent or metastatic disease, at 18 months after surgery. Pathological Findings On gross examination, the resected pancreas contained an encapsulated mass, 7 cm in diameter. After formalin fixation, its cut surface was green, with areas of hemorrhage (Fig. 2). Microscopically, the tumor cells contained abundant eosinophilic cytoplasm with centrally located nuclei that were enlarged and hyperchromatic with minimal nuclear pleomorphism. The tumor cells were arranged in thick trabecular and pseudoglandular patterns, wrapped by sinusoidal vessels (Fig. 3a,b). There was no evidence of a connection of the tumor to the duct system of the pancreas. Numerous bile plugs were found within tumor cells (Fig. 3c). Reticulin stain showed lack of a reticulin framework (Fig. 3d). The sinusoidal vessels were highlighted by CD34 (Fig. 4a). These staining characteristics were similar to those of hepatocellular carcinoma. Immunohistochemical studies showed a membranous staining pattern for CD10, a granular cytoplasmic pattern for hepatocyte antigen, and the typical canalicular pattern for polyclonal CEA (Fig. 4b,c,d). Staining for monoclonal CEA, cytokeratin (CK) 7, CK19, CA19-9, synaptophysin, and alpha-fetoprotein (Fig. 5a) were all negative. Staining for CD68 showed a marked reduction in the number of Kupffer cells (Fig. 5b). Ki-67 staining demonstrated a low proliferative index (1.5%) (Fig. 5c). Staining for p53 was negative (Fig. 5d). Electron microscopic study showed cells with abundant cytoplasmic mitochondria and clusters of rough endoplasmic reticulum (rer), and canaliculi between adjacent tumor cells with presence of microvilli (Fig. 6). There was no evidence of zymogen or neurosecretory granules. The slides were reviewed in consultation with pathologists from the Armed Forces Institute of Pathology (Washington, DC). They favored the diagnosis of hepatoid carcinoma. Discussion The term hepatoid adenocarcinoma was first used in 1985 by Ishikura et al [7] to describe a special type of extrahepatic adenocarcinoma with a striking morphological similarity to hepatocellular carcinoma. Clinically, the neoplasm is characterized by a predilection for older patients, a very aggressive clinical course, and poor survival [8,9]. The majority of patients manifest metastases at the time of diagnosis. The diagnosis of a hepatoid adenocarcinoma depends on recognition of characteristic histological features supported by other evidence linked to hepatic lineage, including alphafetoprotein production, positive immunoreactivity

3 218 Annals of Clinical & Laboratory Science, vol 36, no. 2, 2006 Fig. 3. (a) A well-defined tumor arising within the pancreas (H&E, original magnification x40). (b) Tumor cells with abundant eosinophilic cytoplasm and enlarged, hyperchromatic nuclei show trabecular and pseudoglandular arrangement, wrapped by sinusoidal vessels (H&E, original magnification x200). (c) Bile plugs were identified (H&E, original magnification x400). (d) Loss of reticulin framework (reticulin stain, original magnification x200).

4 Hepatocellular pancreatic tumor 219 to liver synthesized proteins, and in situ hybridization detection of albumin mrna [3]. Most hepatoid carcinomas have been reported in the stomach [10]. Only 6 cases of hepatoid carcinoma of the pancreas have been published to date. A synchronous focus of duct cell carcinoma or malignant glucagonoma or acinar cell carcinoma was identified in 5 cases [1-4], except for the case reported by Hughes et al [5]. In their case, immunohistochemical study implicated hepatocytic differentiation, based on hepatocyte antigen staining. Positive staining for hepatocyte antigen has also been reported in pancreatic adenocarcinoma [11], intraductal oncocytic papillary neoplasm of the pancreas [12], and oncocytic pancreatic endocrine neoplasms [13]. The latter can mimic hepatocellular carcinoma. In our case, the pancreatic tumor exhibited immunoreactivity for hepatocytic differentiation using hepatocyte antigen, CD10, and polyclonal CEA. Immunohistochemical staining was negative for CK7, CK19, and CA19-9, ruling out ductal differentiation. Negativity for synaptophysin and the lack of neuroendocrine granules and zymogen granules by electron microscopic study did not support an endocrine tumor, oncocytic pancreatic endocrine neoplasm, or acinar tumor. It is not surprising that staining for alpha-fetoprotein was negative, in view of the fact that the serum alphafetoprotein was not elevated at the time of diagnosis. Designation as hepatoid carcinoma might not be entirely appropriate in our case, as a synchronous focus of carcinoma arising from pancreatic ductal cells, islet cells, or acinar cells could not be identified. In our opinion, this tumor does not fulfill the criteria for hepatoid carcinoma as described by Ishikura et al [7]. In our case, the tumor cells were arranged in plates more than three cells thick, lined by compressed sinusoid-like capillaries, which were reactive to CD34. Reticulin stain showed lack of a reticulin framework. The staining characteristics were at odds with that of an adenoma, albeit mitotic activity was low and nuclear pleomorphism was minimal. In addition to these features, this tumor demonstrated a marked reduction in the number of Kupffer cells by CD68 stain. Studies have shown that the number of Kupffer cells in cancerous tissue is decreased in comparison to the number in noncancerous tissues [14]. Combining the overall H&E morphology and the results of histochemical and immunohistochemical studies, we are inclined to consider this as a malignant tumor. The low Ki- 67 labeling index and absence of p53 staining suggest a low grade behaviour. The case reported by Cuilliere el al [6] was thought to be a solid adenoma of the pancreas with exclusive hepatocelluar differentiation. Their tumor was considered as benign because of the lack of mitoses, nuclear atypia, and vascular invasion. Reticulin stain and immunostain for CD34 were not performed. It seems uncertain whether the case reported by Cuilliere et al is malignant or not. We considered the possibility that our patient s tumor developed from intrapancreatic heterotopic liver tissue. The heterotopia can occur at various sites near the liver, such as the gallbladder, stomach, hepatic ligaments, omentum, retroperitoneum, and thorax [15]. Despite thorough sampling, we were unable to demonstrate the presence of heterotopic liver tissue in the pancreas. Therefore, heterotopic hepatocellular carcinoma is unlikely. Metastatic hepatocellular carcinoma (HCC) was also considered. The incidence of HCC spreading to the pancreas is only 2.7% to 5.6% and the metastasis usually is a late finding [16]. Clinical work-up of our patient failed to reveal any tumor in the liver. However, long-term follow-up is needed to exclude the possibility that the pancreatic tumor represents a metastasis from the liver. The liver and pancreas share a common embryological origin from the foregut endoderm. Pancreatic cells possess liver-specific genes normally in the repressed state that may be activated during the process of tumorigenesis, leading to a hepatic phenotype. In our case, phenotypical linkage to hepatocytes was established, suggesting the possible transdifferentiation of hepatocytes from pancreatic acinar ductal epithelial cells during tumorigenesis, (Opposite page) Fig. 4 (Immunohistochemical studies, original magnification x400). (a) CD34 highlighted the sinusoidal vessels. (b) Positive membranous staining for CD10. (c) Positive granular cytoplasmic staining for hepatocyte antigen. (d) Positive canalicular staining for polyclonal CEA.

5 220 Annals of Clinical & Laboratory Science, vol 36, no. 2, 2006 Fig. 5 (Immunohistochemical studies, original magnification x400). (a) Negative staining for alpha-fetoprotein. (b) Marked reduction in staining for CD68. (c) Positive nuclear staining for Ki-67 with a labeling index of 1.5%. (d) Negative staining for p53. Fig. 6. (Electron microscopic study). Tumor cells had abundant cytoplasmic mitochondria, clusters of rer, and microvilli. There were no zymogen or neurosecretory granules.

6 Hepatocellular pancreatic tumor 221 which has been demonstrated in an animal model [17]. The possibility of hepatoid tumor arising from pancreatic stem cells can also not be excluded In summary, we report a unique pancreatic tumor with exclusive hepatocellular differentiation. Vigilant follow-up will be required to establish its nature. Acknowledgements We thank Dr. W.-H. Ku for assistance with figures and Dr. K.-J. Kao for proof-reading the manuscript. References 1. Hruban RH, Molina JM, Reddy MN, Boitnott JK. A neoplasm with pancreatic and hepatocellular differentiation presenting with subcutaneous fat necrosis. Am J Clin Pathol 1987;88: Obara T, Takai S, Ayabe T. A case of alpha-fetoprotein producing hepatoid adenocarcinoma of the pancreas. Proc Jpn Cancer Assoc 1988;47: Paner GP, Thompson KS, Reyes CV. Hepatoid carcinoma of the pancreas. Cancer 2000;88: Yano T, Ishikura H, Wada T, Kishimoto T, Kondo S, Katoh H, Yoshiki T. Hepatoid adenocarcinoma of the pancreas. Histopathology 1999;35: Hughes K, Kelty S, Martin R. Hepatoid carcinoma of the pancreas. Am Surg 2004: 70: Cuilliere P, Lazure T, Bui M, Fabre M, Buffet C, Gayral F, Bedossa P. Solid adenoma with exclusive hepatocellular differentiation: a new variant among pancreatic benign neoplasms? Virchows Arch 2002;441: Ishikura H, Fukasawa Y, Ogasawara K, Natori T, Tsukada Y, Aizawa M. An AFP-producing gastric carcinoma with features of hepatic differentiation: a case report. Cancer 1985:56: Chang YC, Nagasue N, Abe S, Kohno H, Kumar DD, Nakamura T. Alpha-fetoprotein producing early gastric cancer with liver metastasis: report of three cases. Gut 1991;32: Ishikura H, Kishimoto T, Andachi H, Kakuta Y, Yoshiki T. Gastrointestinal hepatoid adenocarcinoma: venous permeation and mimicry of hepatocellular carcinoma, a report of four cases. Histopathology 1997;31: Nagai E, Ueyama T, Yao T, Tsuneyoshi M. Hepatoid adenocarcinoma of the stomach: a clinicopathologic and immunohistochemical analysis. Cancer 1993;72: Chu PG, Ishizawa S, Wu E, Weiss L. Hepatocyte antigen as a marker of hepatocellular carcinoma: An immunohistochemical comparison to carcinoembryonic antigen, CD10 and alpha-fetoprotein. Am J Surg Pathol 2002;26: Chung SM, Hruban RH, Iacobuzio-Donahue, Adsay NV, Zee SY, Klimstra DS. Analysis of molecular alterations and differentiation pathways in intraductal oncocytic papillary neoplasm of the pancreas. Mod Pathol 2005;18:279A(suppl). 13. Hussain S, Arwini A, Chetty R, Klimstra DS. Oncocytic pancreatic endocrine neoplasms: A clinicopathologic and immunohistochemical analysis of 21 cases. Mod Pathol 2005;18:279A(suppl). 14. Tanaka M, Nakashima O, Wada Y, Kage M, Kojiro M. Pathomorphological study of Kupffer cells in hepatocellular carcinoma and hyperplastic nodular lesions in the liver. Hepatology 1996;24: Arakawa M, Kimura Y, Sakata K, Kubo Y, Fukushima T, Okuda K. Propensity of ectopic liver to hepatocarcinogenesis: case reports and a review of the literature. Hepatology 1999;29: Lowe CJ, Riepe SP, Wood WC. Hepatocellular carcinoma presenting as a pancreatic head mass: report of an unusual case. Am J Clin Oncol 1997;20: Rao MS, Subbarao V, Reddy JK. Induction of hepatocytes in the pancreas of copper-depleted rats following copper repletion. Cell Diff 1986;18: