Keywords
pancreatic neoplasm - intrapancreatic accessory spleen - endoscopic ultrasound
Incidentally discovered pancreatic cysts have become more common with increasing use
of abdominal cross-sectional imaging. Many of these cysts are benign, while some are
malignant or have malignant potential. Further evaluation and management of asymptomatic
pancreatic cysts depends on its malignant potential. Tools that help us to better
risk stratify a pancreatic cyst include advanced imaging techniques such as pancreatic
protocol computed tomography (CT) scan or magnetic resonance imaging (MRI) with cholangiopancreatography.
Endoscopic ultrasound (EUS) and fine-needle aspiration (FNA) are invasive measures
to better define and sample cysts especially if high-risk features are present. High-risk
features within a cyst, such as nodularity, calcifications, or pancreatic ductal dilatation,
are concerning. These may suggest advanced dysplasia or malignancy. These lesions
are strongly considered for surgical resection due to malignant potential even when
needle aspiration does not demonstrate concerning findings due to the low sensitivity.[1] EUS may also yield pancreatic cyst fluid for analysis of carcinoembryonic antigen
(CEA) which is elevated in mucinous cysts. This case highlights a rare finding of
a mucinous, epidermoid cyst in an intrapancreatic accessory spleen (IPAS) with high-risk
features on EUS.
Case Presentation
This is a 42-year-old African American female who had an incidental finding of a new
17-mm pancreatic tail cystic lesion found on a CT scan during workup for abdominal
pain. Patient was lost to follow-up, until a repeat CT scan 1 year later demonstrated
a stable low attenuation, 15 mm × 11 mm pancreatic tail cyst ([Fig. 1]). She complained of decreased appetite and intermittent epigastric pain over the
last year. She was referred for EUS with FNA for further evaluation of the cyst. Her
history is significant for diabetes mellitus, human immunodeficiency (well-controlled),
alcohol and intermittent substance usage (marijuana and cocaine), recent ventral hernia
repair, and family history significant only for breast and lung cancer. She has no
significant tobacco usage history. No prior episodes of pancreatitis, known pancreatic
disorder, or prior intervention. Exam is otherwise unremarkable, without palpable
mass, jaundice, or tenderness to palpation. The patient underwent an EUS which found
a complex cystic lesion in the pancreatic tail and an abnormal lymph node in the peripancreatic
region ([Fig. 2]). The pancreatic lesion had high-risk features, demonstrating both cystic and atypical
solid components, measuring 27 mm × 9 mm, and abutting the splenic vessels near the
hilum without invasion and a 27 mm × 11 mm enlarged peripancreatic lymph node. Both
were sampled by FNA. Approximately 5 mL of pancreatic cystic fluid was obtained which
appeared cloudy, blood tinged, and viscous. Fluid analysis demonstrated CEA level
of 5,327.7 ng/mL, amylase of 335 U/L, and glucose of 69 mg/dL. Cytology demonstrated
benign appearing squamous cells and a few atypical, degenerated cells. Lymph node
findings were benign. Serum CA 19–9 was low at <3 U/L.
Fig. 1 Pancreatic lesion (arrow) on computed tomography imaging.
Fig. 2 Atypical cystic pancreatic tail lesion on EUS with solid components. EUS, endoscopic
ultrasound.
Given these high-risk findings the patient underwent distal pancreatectomy and splenectomy.
Intraoperative findings included no evidence of distant metastatic disease, no worrisome
lymphadenopathy, and a lesion in the pancreatic tail without invasions into surrounding
tissues. Pathological evaluation demonstrated IPAS with associated benign epithelial-lined
mucinous cyst, without in situ or invasive carcinoma identified. The cyst lining shows
squamoid and apocrine features. No goblet cells are identified. Immunohistochemistry
shows positive staining for CEA in the cyst lining ([Fig. 3]). Twelve benign lymph nodes negative for carcinoma and negative margins. The patient
did well postoperatively and was discharged on postoperative day 6. At outpatient
postoperative visit, she continued to do well and had no ongoing issues with abdominal
pain.
Fig. 3 Pathology of intrapancreatic cyst. (A) Microscopic examination of the distal pancreas shows and intrapancreatic accessory
spleen (arrows) and an associated epithelial cyst (arrowheads, hematoxylin and eosin,
original magnification ×2). (B) Higher power shows a stratified epithelial lining without keratinization. Some cells
abutting the cystic space demonstrate apical nuclei while in other cells there appear
to be cytoplasmic blebs (hematoxylin and eosin, original magnification ×400). (C) The linking epithelial is strongly positive on immunostaining for polyclonal carcinoembryonic
antigen. (immunohistochemistry with DAB chromogen, original magnification ×400). DAB,
3,3′-Diaminobenzidine.
Discussion
IPAS is found in approximately 10% of autopsies. Accessory spleens are due to postoperative
splenosis or ectopic proliferation of splenic tissue during fetal development.[2] IPAS may frequently be detected as a nodule on CT and MRI imaging characterized
similar to the spleen on precontrast and contrast-enhanced imaging modalities.[3] Similarly on ultrasound imaging, accessory spleens are echogenically similar to
the main spleen and are round or oval with presence of vascular hilum on Doppler ultrasound.[4] Other studies have suggested the usage of contrast-enhanced EUS and EUS-elastography
as a useful tool for diagnosis of IPAS.[5] Appearance of the lesion in this case was a very unusual presentation for anIPAS,
given its association within a mucinous cyst. This is a rare diagnosis with less than
60 reported cases. Malignant potential is unknown; however, there is a report of squamous
cell carcinoma arising in an epithelioid cyst within the spleen.[6]
Epithelial cysts in IPAS is rare with half of these reported incidentally detected.
Zavras et al reviewed 36 patients and found the mean age of patients to be 46 years
and slightly over half were female. Patients were asymptomatic or complained of abdominal
or epigastric pain. The cysts were all located in the tail of the pancreas and ranged
in size from 1.4 to 12.6 cm. Serum CEA and CA 19–9 levels were normal in the majority
of patient and immunohistochemistry demonstrated positivity for CEA in the cyst lining.[7] Similar findings were found in this case. Her serum CEA was normal and immunohistochemistry
was positive staining for CEA. Epithelial cysts of the spleen demonstrate an epithelial
lining of low cuboidal, low columnar, or squamous type, surrounded by splenic tissue.[8] The cyst lining of epithelial cysts in IPAS shows similar histology which was also
found in our patient.
Fluid analysis and serum biomarkers are widely used for the evaluation of pancreatic
masses. However, the efficacy of fluid studies continues to be poorly demonstrated
in IPAS with less than 20% of cases reporting fluid biomarkers.[9]
[10] Li et al conduced a systematic review of 56 patients with epidermoid cysts in IPAS
and found 9 of 9 patients with an elevated cyst fluid CEA and 1 of 6 patients with
an elevated fluid CA 19–9. Serum CEA was normal in 26 patients compared with only
one patient with an elevated serum CEA. Reported serum CA 19–9 levels were elevated
in 20 of 37 patients.[11] Despite these findings, there is insufficient data to conclude significance of these
biomarkers in epidermoid cystic IPAS.
Appropriate management of mucinous epidermoid cyst in IPAS has not been established.
A study in Spain found four cases of IPAS that were diagnosed with EUS and FNA which
were safety followed with imaging studies.[12] However, all reported cases of epidermal cysts in IPAS have undergone surgical resection
or excision.[13] Conservative management of these lesions has yet to be reported or studied.
Conclusion
In conclusion, IPAS within a mucinous epithelioid cyst is a rare entity in the literature.
Imaging and endoscopic evaluation may be helpful in the diagnosis; however, there
continues to be little information of appropriate management. Specific biomarkers
have yet to identify to separate IPAS from other malignant potential mucinous cysts
of the pancreas. Future case series regarding radiographic imaging, cystic features,
and specific fluid biomarkers may be required to fully understand Epidermoid Cyst
in IPAS and identify malignant potential.
