Lymphoepithelial
cyst of the pancreas. A case report
L
Fraser, OO Komolafe, JR Anderson
Department
of Surgery, Southern General Hospital, Glasgow, UK
Corresponding
Author
Mr
Segun Komolafe
skomolafe@yahoo.co.uk
Abstract
We
present the case of a 63 year-old male who presented with a cystic lesion of the
distal pancreas. Excision and
histology showed this to be a lymphoepithelial cyst.
Cystic lesions of the pancreas represent a diagnostic challenge,
especially when pseudocyst secondary to pancreatitis is excluded. These lesions
can be broadly classified into benign, pre-malignant and malignant. Widely used
imaging modalities such as CT and MRI are not able to categorically
differentiate between these. More invasive procedures such as endoscopic US and
FNA again do not give a cast-iron diagnosis. Our patient had a symptomatic
cystic lesion in his pancreas which was excised after cross-specialty
discussion. We advocate that this is the ideal way to treat patients with cystic
lesions of the pancreas, with each case considered on its own merits as all
current diagnostic investigations have their limitations.
Keywords:
Lymphoepithelial cyst; pancreatic cyst; distal pancreatectomy.
Abbreviations:
CA 19-9 – Carbohydrate Antigen 19-9; CEA – Carcinoembryonic Antigen; CT –
Computerised Tomography; FNA – Fine Needle Aspiration; LEC –
Lymphoepithelial Cyst; MRI – Magnetic Resonance Imaging; US – Ultrasound.
Case Report
A
63-year-old gentleman was referred to our surgical outpatient clinic with a 2
month history of post-prandial vomiting and weight loss. He had a past medical
history of ischaemic heart disease. On examination he was found to have a
diffuse epigastric mass. All blood tests were normal. Ultrasound examination showed a 12.5 x 9cm cystic lesion
arising from the tail of the pancreas. CT examination (Fig
1) revealed that this lesion was closely related to the body of
pancreas and posterior wall of the stomach. There was no surrounding
infiltration, no lymphadenopathy and no liver
metastases seen. Upper GI endoscopy was normal to the second part of the
duodenum without any distortion of the posterior wall of the stomach. On MRI
scanning (Fig
2) the lesion had a homogenous signal, suggesting it was mucinous.
The
patient was discussed at a multi-disciplinary
(surgery–radiology–oncology–pathology) meeting. The consensus was that the
lesion was most likely a mucinous cystadenoma which ought to be excised. It was
also concluded that in this instance, endoscopic ultrasound would not change
management, and was therefore not carried out. After anaesthetic review he was
admitted electively for surgery. Laparotomy through a rooftop incision was
performed and the cyst, arising from the body of the pancreas, was identified.
The spleen was mobilised together with the tail and body of the pancreas and a
distal pancreatectomy with en-bloc splenectomy was carried out.
The
patient made an unremarkable recovery over the next few days and was due for
discharge on the 5th post-operative day. Unfortunately, he had a
sudden collapse the night before his discharge, and attempts at resuscitation
were unsuccessful. His family did not consent to a post-mortem examination so
the presumed cause of death was cardiac arrest secondary to myocardial
infarction or pulmonary embolus. Pathological examination of the resected
specimen revealed a cystic mass measuring 14.5 x 13.5 x 7cm arising from the
body of the pancreas. Microscopy showed a cyst lined by keratinising squamous
epithelium with underlying lymphoid tissue including germinal centres suggestive
of a lymphoepithelial cyst of the pancreas (Fig
3). The cyst had been completely excised.
Discussion
Cystic
lesions of the pancreas encompass a broad spectrum of pathologies and several
classification systems exist. These include those taking into account
histological findings1 – true cyst vs. pseudocyst; aetiology2
– congenital vs. acquired; or radiological appearances3 – serous
vs. mucinous. We found the most useful classification to be the simple division
of cystic pancreatic lesions into benign, pre-malignant and malignant,4
because of the obvious clinical implications. With improvement in the resolution
of cross-sectional imaging, more cystic lesions of the pancreas are being
detected. This often creates a dilemma as none of the investigative modalities
can be entirely relied upon to identify malignant or pre-malignant lesions which
require intervention and benign lesions which do not.
Diagnosis
can be obvious as in a pseudocyst forming after a recent episode of acute
pancreatitis, or an infiltrating mucinous cystadenocarcinoma. However the
numerous other cystic lesions of the pancreas can look similar on CT and MRI
images3. Invasive tests such as endoscopic ultrasound with fine
needle aspiration can be helpful in giving more detail, and obtaining fluid for
cytological and biochemical analysis.5 These invasive tests however
do not always help with diagnosis, carry attendant risks for morbidity and
mortality, as well as the theoretical risk of tumour seeding if malignant cells
are spilled.6 If there is reasonable doubt about the nature of a
cystic lesion which is thought not to be a pseudocyst, most authorities
recommend excision.4
Lymphoepithelial
cysts (LEC) constitute a rare and benign entity. Unlike pseudocysts which have
fibrous walls, LEC are true cysts with an epithelial lining.7 They
are typically characterised by the presence of a squamous epithelium which is
sometimes keratinising, and a dense lymphoid infiltrate.8 LEC were
first described in 1985 by Luchtrath and Schriefers.2 Since then
cases have sporadically been described in the literature.9 They are
usually encapsulated by a well-defined wall and are separated from the
underlying pancreas by a thin fibrous capsule. The yellowish viscous content of
the cyst is accounted for by the presence of keratin, a feature not seen in
other types of pancreatic cysts, except for dermoid cysts.
Lymphoepithelial
cysts often arise in the body and tail of the pancreas and may be multilocular
(60%) or unilocular (40%).7 80%
of the reported cases are in adults over the age of 40, with a 4:1 male to
female ratio.10 Approximately 50% of cases are incidental findings11
and 50%, as with this patient, suffer symptoms such as abdominal pain, nausea,
vomiting, diarrhoea, weight loss and fatigue.
The size of LECs varies and in a series of 12 cases, was found to range
from 1.2 to 17cm (mean 4.8cm).9 The pathogenesis of lymphoepithelial
cysts of the pancreas is still uncertain. Several
hypotheses8 have been proposed including:
š
Squamous metaplasia of an obstructed and dilated pancreatic duct
š
Misplacement of remnants of the branchial cleft in the pancreas during
embryogenesis
š
Intrapancreatic accessory spleen
š
Epstein–Barr virus
š
Lesions caused by lymphoid cells with an affinity for ductal epithelia
and the capacity to induce epithelial proliferation.
š
Ectopic pancreatic tissue included in a peripancreatic lymph node
Ultrasonography,
CT and MRI are all helpful in defining the size and consistency of the lesion,
but do not conclusively distinguish LEC from other benign or malignant cystic
neoplasms pre-operatively. Endoscopic
FNA for biochemical and cytological analysis has also been proposed as a method
for helping reach the diagnosis of LEC pre-operatively.12 Biochemical
analysis of aspirated fluid have shown high levels of tumour markers (CEA, CA
19-9) but these are comparable to levels found in malignant pancreatic lesions,
so these tests are not specific. The presence of squamous cells, keratinous
debris and lymphoid tissue in aspirated fluid points towards LEC. As mentioned
earlier however, there is still the risk of seeding of tumour cells should the
lesion not turn out to be benign. Because of this diagnostic uncertainty,
surgical resection is usually undertaken. Several surgical treatments have been
used in patients with lymphoepithelial cysts; these range from simple excision
of the lesion to more radical procedures such as distal pancreatectomy with or
without splenectomy or cephalic pancreaticoduodenectomy.
In
summary, lymphoepithelial cysts are rare, benign true pancreatic cysts.
Preoperative diagnosis is difficult, and it is hard to rule out a
malignant or pre-malignant lesion with currently available tests. Our patient
had a symptomatic cystic lesion of his pancreas completely excised in view of
diagnostic uncertainty. As there is no definitive investigation, we suggest that
each cystic lesion of the pancreas be dealt with on its own merit, and ideally
in a multi-disciplinary setting.
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