Mini Review
Solid-Pseudopapillary Neoplasm, Pancreas: A Pathologist’s Perspective
Sood Neelam*
Department of Pathology and Lab medicine, Deen Dayal Upadhyay Hospital, India
*Corresponding author: Sood Neelam, Department of Pathology and Lab medicine, Deen Dayal Upadhyay Hospital, India
Published: 13 May, 2018
Cite this article as: Neelam S. Solid-Pseudopapillary
Neoplasm, Pancreas: A Pathologist’s
Perspective. Clin Oncol. 2018; 3: 1460.
Introduction
Solid-pseudopapillary neoplasm of the pancreas is an uncommon tumor, which lately has
attracted a lot of attention. Typically it is seen more often in young women. Not only does it have
nonspecific clinical and radiologic manifestations, but has an equally enigmatic nature. It was
earlier considered benign, however now it is currently considered a low-grade malignant epithelial
neoplasm with low metastatic rate as well as high overall survival rate. It accounts for approximately
1% to 2% of all exocrine pancreatic tumors. Its synonyms are Solid-cystic tumor, papillary-cystic
tumor, solid and papillary epithelial neoplasm, low-grade papillary neoplasm, Hamoudi tumor, and
Frantz tumor. The most accepted terminology is SPT/SPN, as coined by WHO. It more frequently
affects adolescent girls and young women (mean 35 years) are. It is rare in men and shows no
apparent ethnic preference. Despite the strong gender difference, the tumor has no known genetic,
hormonal or any endocrine disturbances [1,2].
Till date, the available information on SPN are mostly available from individual case reports
and small series. As of now, more than 750 cases have been reported in the English literature, that
too mostly within the last 20 years, reflecting thereby the increased awareness of this uncommon
neoplasm [1,3,4].
The phenotype of these tumors is poorly understood, and these neoplastic cells are not clearly
related to any of the well characterized cells of the pancreas and has been postulated to arise from
primitive pancreatic cells, which could be acinar cells, ductal epithelial, endocrine cells or even
pluripotent cells [5,6]. Female genital buds have also been implicated. Cell lines from despite this,
clonality of this tumor has been lately confirmed [1,5-8].
Usually, these neoplasms are incidental in patients presenting with nonspecific complaints of
abdominal discomfort and pain, occasionally after abdominal trauma. Even where these tumours
arise from the head of the pancreas, there is no associated functional endocrine syndrome. All the
known tumour markers are normal. Computed Tomography (CT) shows a well demarcated, mass,
variably solid and cystic, but without any internal septations. Calcifications may be noted at the
margins. These lesions are usually hypovascular or mildly hypervascular [4,9-11].
Pathology
Since this tumor has an excellent prognosis as compared to neuroendocrine and acinar cell
carcinoma, the close morphologic differential diagnoses, it is crucial to diagnose SPTP correctly.
Endoscopic/ultrasound-guided/Computed Tomography (CT)-guided FNA, using a panel of
immunohistochemical staining on cell block preparations can be of tremendous help in establishing
right preoperative diagnosis. The smears are usually cellular showing cell clusters in delicate papillary
fronds with branching capillaries or sometimes only as nonspecific cell clusters. The tumor cells are
bland and uniform with moderate cytoplasm. The nuclei are round to oval with finely granular
chromatin. Cytoplasmic eosinophilic hyaline globules, large clear cytoplasmic vacuoles, nuclear
grooving, and myxoid stroma have been variably described [12-16].
SPN shows no predilection for any specific location, although tail has been report frequent
site [3,4,17]. The tumors size may vary from 0.5 cm to 34.5 cm. Larger lesions characteristically
have a solid and cystic appearance, whereas smaller lesions are usually more solid but less sharply
circumscribed as compared to larger lesions. Larger lesions usually have a fibrous pseudo capsule
and a variegated cut surface, showing friable and cystic degeneration and hemorrhage, on the other
hand smaller lesions are less delineated. In presence of extensive cystic degeneration, it may simulate
a pseudo cyst [3,17,18].
SPN shows vascular zones of polygonal epithelial cells alternating
with cystic spaces. The characteristic pseudopapillary appearance is
due to degenerative changes resulting in tumor cell discohesion. As
the lesion is highly vascular the capillary-sized vessels surrounded by
a cuff of neoplastic cells having scanty cytoplasm, resemble papillae
[17,18].
The cells have abundant eosinophilic cytoplasm with uniform,
round to oval, nuclei lacking the endocrine salt-and-pepper type of
chromatin. Nuclear grooves can be invariably seen. These cells show
low mitotic activity. Clear cell variants with vacuolated cytoplasm
have also been described, which is attributed to the distended
mitochondria and endoplasmic reticulum [19]. Focal aggregation of
intracytoplasmic and extracytoplasmic hyaline globules have been
usually described, which are periodic acid-Schiff positive and diastase
resistant [17,18]. Foamy macrophages, hemorrhage, and cholesterol
clefts, myxoid change and microcalcifications, are other features
noted ,attributed to degenerative changes. Malignant transformation
and focal sarcomatoid component is very rare with occasional case
reports, which may show diffuse growth with more cellular atypia,
tumor necrosis, and high mitotic activity. Local infiltration into
adjacent structures, perineural invasion as well as vascular invasion
may sometimes be seen, despite indolent behavior [4,11].
Recent Advances
Solid-pseudopapillary neoplasm has been tested for numerous
immunohistochemical markers and has been equally enigmatic.
In recent reports, most SPNs demonstrated nuclear localization
of β-catenin and loss of membrane expression of E-cadherin
with disruption of the activated Wnt pathway [20-24]. Another
consequence of this disruption is cyclin D1 over expression [21]. In
addition, results for CD10 are positive in a significant number of cases
and neuroendocrine markers have been seen to be variably expressed
in SPN [22,25]. With the exception of the consistently negative results
for chromogranin A, variable expression of other neuroendocrine
markers, that is, synaptophysin, neuron-specific enolase, and
CD56, was demonstrated. This staining profile thus complicates the
differentiation of SPN from pancreatic neuroendocrine tumor, which
is the most important entity in its differential diagnosis. CytoKeratins
(CK), i.e. pancytokeratin, CK8 and CK18 are also variably expressed
[25]. However, CK7 and CK19 are mostly negative [20,25]. Solidpseudopapillary
neoplasm also stains for vimentin, progesterone
receptor, and estrogen receptor β (but not estrogen receptor α),
there by supporting genital ridge theory of its origin [7]. DOG1
has been demonstrated in some reports and has been found to be
a novel marker for centroacinar cells and for solid-pseudopapillary
neoplasms, which on the other hand is suggestive of a centroacinar
origin of these neoplasms [26] Stains for α1-antitrypsin are positive,
highlighting the periodic acid-Schiff-positive hyaline globules, and
are negative for pancreatic enzymes [25,27]. Other sporadic reported
stains include DPC4, CD117, p21, p27, and to a lesser extent, p16
[21,28]. Expression of Ki-67 is usually low, although it was reported
to be high in clinically aggressive cases only [29]. Other markers, such
as carcinoembryonic antigen and CA 19.9, are not expressed [27].
This lesion having generated so much interest recently, definitely
needs a detailed evaluation with complete IHC support to give the
patient the desired benefits.
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