1Intrapancreatic splenic peliosis

Ann. Cancer Res. Ther. Vol. 23, No. 1, pp. 1-4, 2015

Introduction

Approximately 10% of the population will have an accessory spleen in various parts of the body1). When an accessory spleen arises from the pancreatic tail, it oc-casionally mimics pancreatic solid tumors2-4), resulting in unnecessary surgical resection. However, because of recent developments in radiological diagnostic modali-ties and in our understanding of this condition, careful follow-up is now starting to be chosen first, rather than surgery.

However, when the accessory spleen is accompanied by cystic changes, diagnosing the lesion becomes quite challenging. One of the differential diagnoses of cystic lesions is epithelial (epidermoid) cysts formed in the in-trapancreatic heterotopic spleen5-10). A literature review of previous cases suggests that radiological findings vary among cases and that the condition often mimics mu-cinous cystic neoplasm (MCN), in that both have thick walls, a solid component (similar to mural nodules), and

no communication with the pancreatic duct, and patients have elevated serum CA19-9 levels5). Unfortunately, pa-tients are often treated with surgery, despite the fact that specific treatment is not required for asymptomatic epi-thelial cysts5-10).

Another differential diagnosis of cystic lesions in the pancreatic tail could be peliosis of the intrapancreatic spleen11, 12). Peliosis is also quite a rare condition and is characterized by multiple cyst-like blood-filled cavities. Peliosis occurs most commonly in the liver and rarely in the spleen. The pathogenesis, natural history, and treat-ment of splenic peliosis remain unclear, and the accumu-lation of information from more cases is necessary for a better understanding of this rare condition.

Case presentation

A 44-year-old Japanese man with a medical history of chronic hepatitis C virus infection was referred for the treatment of a pancreatic cystic lesion. When the patient was 42 years of age, abdominal ultrasonography (US) first identified a 1.8-cm cystic mass lesion arising from the pancreatic tail. Although the lesion had been fol-lowed-up as a benign pancreatic cyst, the most recent ab-dominal US indicated that the mass lesion had increased

Case Report

A case of Peliosis and epithelial cyst of intrapancreatic heterotopic spleen: a differential diagnosis of pancreatic mucinous cystic neoplasm

Toyokazu Akimori1), Hiromichi Maeda2), Ken Okamoto2), Tsutomu Namikawa3), Takashi Usui4), Kazuhiro Hanazaki3), Michiya Kobayashi2)

Hata Kenmin Hospital, Department of Surgery1), Cancer Treatment Center, Kochi Medical School2), Department of Surgery, Kochi Medical School3), Tano Hospital, Tano-cho, Japan4)

AbstractBackground: Peliosis is characterized by multiple cyst-like blood-filled cavities, and is potentially hazardous because of the possibility of spontaneous rupture. Herein, we describe a patient with ectopic spleen accompanied by peliosis and epi-thelial cyst, which mimicked a pancreatic cystic neoplasm.Case: A 44-year-old asymptomatic male patient was referred for treatment of an enlarged mass in the pancreatic tail. Abdominal computed tomography and magnetic resonance imaging revealed a 3.5-cm cystic lesion with a clear, thick, and smooth cyst wall, which was enhanced by contrast media. Under a tentative diagnosis of mucinous cystic neoplasm of the pancreas, the patient underwent distal pancreatectomy. Postoperative pathological examination identified the lesions as peliosis and epithelial cyst of the intrapancreatic heterotopic spleen.Conclusion: Cystic formations in the intrapancreatic spleen mimic mucin-producing neoplastic lesions and can be misdiag-nosed. Peliosis may cause rapid growth of the cysts, mistakenly indicating a malignant potential of the lesion.

Key Words: ectopic spleen, peliosis, epithelial cyst, heterotopic spleen

(Received March 19, 2015; Accepted March 26, 2015)

Correspondence to : Hiromichi Maeda, MD, PhD. Cancer Treatment Center, Kochi Medical School Hospital, Kochi University, Kohasu, Oko-cho, Nankoku, Kochi, 783-8505, Japan. TEL: +81-88-880-2370, Fax: +81-88-880-2371, E-mail: hmaeda@kochi-u.ac.jp

2 Annals of Cancer Research and Therapy Vol. 23 No. 1, 2015

over a period of 10 months to a maximum diameter of 3.2 cm.

The patient did not have a history of pancreatitis, ab-dominal trauma, alcohol abuse, or other drug abuse. The patient was asymptomatic and physical examination was unremarkable. Laboratory studies revealed hepatobiliary, pancreatic enzyme, and tumor markers all within the normal range. Contrast-enhanced abdominal computed tomography (CT) revealed a 3.5-cm oval cystic lesion with a clear, thick, and smooth wall in the pancreatic tail. The cyst wall was mildly enhanced, whereas the in-ner part of the cyst was not (Fig. 1). Magnetic resonance imaging revealed high signal intensity for the inner con-tents of the cyst on T1-weighted images and low signal intensity on T2-weighted images, suggesting a mucinous element (Fig. 2A, B). T1-weighted imaging clearly dem-onstrated the septum of the cyst, which was not clear on CT scans. Although preoperative endoscopic ultrasound revealed the septum of the cyst, the result was not diag-

nostic. There was no communication between the main pancreatic duct and the cyst identified on endoscopic retrograde cholangiopancreatography, and the lesion was diagnosed as MCN of the pancreatic tail. The patient underwent distal pancreatectomy because of the malig-nant potential of the lesion (based on the increase in size of the cystic tumor and the nodule within the cyst). Fine needle aspiration biopsy was not performed because of the potential risk of implanting malignant cells along the biopsy needle.

On laparotomy, intraoperative US showed a well-demarcated round mass in the pancreatic tail with septa (Fig. 3). On the resected specimen, the cystic lesion was dark red in color and filled with fluid (Fig. 4A). The cyst was multilobular with a red colored inner surface and filled with old blood (Fig. 4B). Pathologically, the cyst was located in the intrapancreatic accessory spleen. There were also other cystic lesions filled with old blood but without an apparent epithelial lining (Fig. 5). The

Fig. 1 Abdominal enhanced computed tomography (A) The pancreatic cystic lesion has a relatively thick

wall with enhancement (white arrow). (B) The cystic lesion is arising from the pancreatic

parenchyma.

Fig. 2 T1- and T2-weighted images TMagnetic resonance imaging revealed high sig-

nal intensity for the components of the cyst on T1-weighted images (A) and low signal intensity on T2-weighted images (B), suggesting the presence of mucinous material or old blood within the cyst. The solid component or septa of the cyst could be seen on T1-weighted images (white arrow).

3Intrapancreatic splenic peliosis

Fig. 3 Intraoperative ultrasound The contents of some cavities were highly echogenic

(white arrowhead), whereas others had low echo-genicity. The septa of the cyst are indicated by the white arrow.

Fig. 4 Resected specimen of the pancreatic cystic lesion (A) The external aspect of the lesion is dark red (black

arrow). (B) The cross-section of the specimen reveals that

some of the cysts are filled with old blood. The cyst is surrounded by pancreatic tissue with fi-

brous changes (black arrow).

Fig. 5 Pathological examination (A) The whole structure of the lesion. There are sev-

eral cavities filled with blood that are not lined by epithelial cells, which is diagnosed as peliosis (P). Other cystic lesions are lined with epithelial cells (small arrow head) and diagnosed as epithelial cysts. The whole cystic lesion is surrounded by pancreatic tissue with fibrous changes and adja-cent to normal pancreatic tissue.

(B) The epithelial cyst is surrounded by columnar epithelium. The thin layer of ectopic tissue is comprised of lymphoid tissue with a germinal center (arrow), sinusoid, and hyalinized fibrous tissue (arrowhead).

(C) The markedly dilated blood-filled spaces (pelio-sis) lack an endothelial lining.

4 Annals of Cancer Research and Therapy Vol. 23 No. 1, 2015

final pathological diagnosis was peliosis and epithelial cyst of the intrapancreatic accessory spleen without ma-lignant change.

Discussion

Approximately 10% of the population will have an ac-cessory spleen in various parts of the body, including the wall of the jejunum, mesentery, pelvis, and intrapancre-as1). However, formation of an epithelial cyst in an acces-sory spleen in the pancreatic tail is very rare and difficult to diagnose preoperatively. Occasionally, malignancy may be suspected because of the solid component of the cyst and elevated CA19-9 levels5), even though malignant changes of epithelial cysts have not been reported13). It may be possible to correctly diagnose these cysts pre-operatively if the solid part of the lesion is of the same intensity as the splenic tissue on CT or MRI. However, when the ectopic splenic tissue is very thin, as in the present case, it resembles the thick wall of neoplastic cystic lesions, making preoperative diagnosis difficult.

In the current case, the cystic lesion was preopera-tively diagnosed as MCNs because it had a characteristic features of MCNs14), such as a thick-walled single cyst occurring in the neck to tail of the pancreas, and forma-tion of septa. However, MCNs are predominantly identi-fied in female patients, leaving the other differential di-agnosis to be considered. Intraductal papillary mucinous neoplasm (IPMN) of pancreas could be one of them. However, the radiological evaluation of present case did not show dilated main pancreatic duct, bulging of papilla of Vater, communication of pancreatic duct and cysts, multilobular or multifocal cysts. Thus, the cystic lesion in the present case was tentatively diagnosed as MCN of pancreas harboring possibility of malignant change rather than IPMNs or other epithelial and non-epithelial benign pancreatic cysts15).

On pathological examination of the present case, some cystic lesions were identified as peliosis, which is characterized by multiple cyst-like blood-filled cavi-ties within the parenchyma of solid organs. The isolated occurrence of splenic peliosis is quite rare and poorly understood11, 12, 16, 17). We consider that peliosis develop-ing in the intrapancreatic accessory spleen is even rarer, and quite difficult to diagnose preoperatively. Peliosis is often described in association with chronic hepatitis C virus, tuberculosis, intravenous drug abuse, chronic alcoholism, hematological malignancies, chemotherapy, or steroid treatment12). Although these condition have been proposed as potential risk factors for peliosis, no solid conclusions have been made as yet. The natural his-tory of peliosis is unclear, and the role of surgery in its treatment has not been determined. However, all patients diagnosed as having peliosis should be provided with information and managed carefully because the sponta-

neous rupture of peliosis, a potentially life-threatening event, has been reported16, 17).

In conclusion, we report on our experience of a pa-tient with rare coexisting peliosis and epithelial cyst in the intrapancreatic accessory spleen. The rapid growth of the pancreatic cystic lesion, possibly due to the pelio-sis, mistakenly indicated malignant potential, resulting in surgical treatment. A greater understanding of these rare diseases and the development of accurate diagnostic techniques are necessary to reduce unnecessary surgery in patients with pancreatic cystic lesions.

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