Neuroendocrine tumors (NETs) are a group of neoplasms that arise from the neural crest. They can be predominantly found in the gastrointestinal tract, pancreas, lung and rarely in the ovary and thymus. The introduction of β emitting 68Ga-radiolabelled-DOTA peptides in PET–CT for the imaging of NETs has been giving promising results. But, it is worthwhile to know the limitations of using Ga-DOTA peptides to minimize the occurrence of false positives. We report an interesting case of a primary mesenteric neuroendocrine tumor that was misdiagnosed as a nodal secondary from a falsely localized primary pancreatic NET as a result of non-specific physiologic Ga-DOTA uptake in the pancreas. This resulted in an unnecessary distal pancreatectomy.

1.
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2. Case Report
False positive localization of primary mesenteric
neuroendocrine tumor to the pancreas with
Ga-DOTATATE PETeCT changing the surgical
management
Rochita Venkata Ramanan a,
*, Manish Chandra Varma b
,
Arunachalam Pudhiavan a
a
Department of Radiology, Apollo Hospitals, Chennai, Tamil Nadu, India
b
Department of Liver Disease and Transplant, Apollo Hospitals, Chennai, Tamil Nadu, India
a r t i c l e i n f o
Article history:
Received 5 April 2014
Accepted 1 May 2014
Available online 24 May 2014
Keywords:
Neuroendocrine tumors
Pancreas
Primary mesenteric
Ga-DOTA PETeCT
False positive
a b s t r a c t
Neuroendocrine tumors (NETs) are a group of neoplasms that arise from the neural crest.
They can be predominantly found in the gastrointestinal tract, pancreas, lung and rarely in
the ovary and thymus.
The introduction of b emitting 68
Ga-radiolabelled-DOTA peptides in PETeCT for the
imaging of NETs has been giving promising results. But, it is worthwhile to know the
limitations of using Ga-DOTA peptides to minimize the occurrence of false positives. We
report an interesting case of a primary mesenteric neuroendocrine tumor that was mis-
diagnosed as a nodal secondary from a falsely localized primary pancreatic NET as a result
of non-specific physiologic Ga-DOTA uptake in the pancreas. This resulted in an unnec-
essary distal pancreatectomy.
Copyright ª 2014, Indraprastha Medical Corporation Ltd. All rights reserved.
1. Introduction
Neuroendocrine tumors (NETs) are a group of neoplasms that
arise from the neural crest. They can be predominantly found
in the gastrointestinal tract, pancreas, lung and rarely in the
ovary and thymus.
The introduction of b emitting 68
Ga-radiolebelled-DOTA
peptides in PETeCT for the imaging of NETs has been giving
promising results. But, it is worthwhile to know the limitations
of using Ga-DOTA peptides to minimize the occurrence of false
positives. We report an interesting case of a primary mesen-
teric neuroendocrine tumor that was misdiagnosed as a nodal
secondary from a primary pancreatic NET as a result of non-
specific Ga-DOTA uptake in the pancreas.
2. Case report
We report the case of a 59-year-old female patient, who pre-
sented with complaints of pain in the epigastric region and
chest along with dysphagia for two months. An abdominal
* Corresponding author. No 34 Srinivasa Moorthy Avenue, Off L B Road, Adyar, Chennai, Tamil Nadu 600020, India.
E-mail address: rochitav@yahoo.com (R.V. Ramanan).
Available online at www.sciencedirect.com
ScienceDirect
journal homepage: www.elsevier.com/locate/apme
a p o l l o m e d i c i n e 1 1 ( 2 0 1 4 ) 1 3 1 e1 3 3
http://dx.doi.org/10.1016/j.apme.2014.05.007
0976-0016/Copyright ª 2014, Indraprastha Medical Corporation Ltd. All rights reserved.

3. ultrasound revealed a spherical hypoechoic mass with
hyperechoic areas in the periphery at the epigastric region,
below and close to the pancreatic body.
This was followed by a contrast enhanced 160 slice helical
CT in the arterial and venous phases. It showed a spherical
solid mass with heterogeneous contrast enhancement
adherent to the duodeno-jejunal flexure and at one point
infiltrating the wall of the jejunum. The mass showed few
calcific foci and hypodense areas within it. The mass was
separate from the pancreas and no focal lesion was found in
the pancreas other than a small cyst in the body. A diagnosis
of gastrointestinal stromal tumor was made on the CT scan.
(Figs. 1 and 2) Guided biopsy of the mass revealed a NET.
It was then decided to perform a Ga-DOTATATE PETeCT.
This showed an increased tracer uptake by the mass with a
SUVmax of 40. In addition, a small area of increased tracer
uptake was also seen in the pancreatic tail region with a
SUVmax of 4.5. (Fig. 3) No corresponding lesion could be
identified on the CT scan. Nevertheless a final diagnosis of a
primary pancreatic NET with adjacent nodal secondaries was
made. Accordingly, the surgical management was changed
from only a wide resection of the mass to a subtotal distal
pancreatectomy with en bloc removal of the mass with
spleen, third and fourth parts of the duodenum and the
proximal jejunum. (Fig. 4).
Histopathology of the mesenteric mass established it to be
a well-differentiated primary mesenteric NET. The resected
pancreatic parenchyma was normal and no lesion corre-
sponding to the increased tracer uptake in the PETeCT ex-
amination could be identified.
3. Discussion
Somatostatin is a small, cyclic neuropeptide that is present in
neurons and endocrine cells. It has a high density in the brain,
peripheral neurons, endocrine pancreas and gastrointestinal
tract.
Fig. 1 e Oblique volume rendered CT reconstruction in the
arterial phase reveals a mass inferior to and separate from
the pancreas.
Fig. 2 e Oblique volume rendered CT reconstruction in the
venous phase reveals the mass close to the first loop of the
jejunum and separate from the pancreas. P-Body pancreas,
H-Head pancreas, St-Stomach.
Fig. 3 e Ga DOTATATE PETeCT reveals a focal increased
uptake in the tail pancreas marked within cursors.
a p o l l o m e d i c i n e 1 1 ( 2 0 1 4 ) 1 3 1 e1 3 3132

4. The rationale for employment of Ga-DOTA-conjugate pep-
tides in the assessment of SST-receptor (SSTR) expressing NET
relies on the high affinity of these compounds for SSTR.
Ga-DOTA-TATE presents a predominant affinity for SSTR 2.
Although PET with the newer Ga-DOTA-conjugate peptides like
Ga-DOTA-TOC, Ga-DOTA-NOC, Ga-DOTA-TATE has brought
about dramatic improvements in spatial resolution compared
to the older I-123 and In-111 labeled studies, there are some
limitations in organs with a higher physiological uptake.
The pancreas shows variable uptake of Ga-DOTA-
conjugate peptides. Though all 5 subtypes of SSTR are pre-
sent in the pancreas, the subtype-2 receptor is commonly
found and is located in the islets. Accumulation of islets in one
pancreatic region, frequently the pancreatic head, may cause
an increased uptake mimicking a tumor.
Any area of focal increased uptake that is not physiological
and has a high SUV is considered diagnostic for tumors. The
median SUVmax values are 59.4 Æ 48.6 for pancreatic NETs,
26.5 Æ 18.6 for gastrointestinal NETs and 20.4 Æ 13.5 for lung
NETs.1
Castellucci et al, in their study have found that in cases of
extra-pancreatic NET, several patients showed increased
pancreatic DOTA uptake, either focal or diffuse.2
Since this
uptake remained stable over a period of follow up, they
concluded that this uptake was likely due to physiologic
variability in SSTR expression by pancreatic endocrine cells
and to variability in their anatomic distribution in the organ.
Awareness of this physiologic variability in SSTR expression
and endocrine cell distribution within the pancreas is impor-
tant especially to avoid misdiagnosis of a tumor.
In our case, this kind of misinterpretation led to an un-
necessary resection of the tail pancreas. The fact that the NET
was closely related to the tail pancreas also contributed to
misdiagnosis. This can be avoided by noting the SUVmax
value of physiologic uptake within normal pancreatic tissue,
which is significantly lower than that of NET. This case
highlights the phenomenon of non-specific physiological Ga-
DOTATATE uptake by pancreatic tissue, which can result in
false positive interpretations and the method to prevent such
an error.
Conflicts of interest
The authors declare no conflict of interest whatsoever arising
out of the publication of this manuscript.
r e f e r e n c e s
1. Campana Davide, Ambrosini Valentina, Pezzilli Raffaele, et al.
Standardized uptake values of 68
Ga-DOTANOC PET: a
promising prognostic tool in neuroendocrine tumors. J Nucl
Med. 2010;51:353e359.
2. Castellucci Paolo, Pou Ucha Javier, Fuccio Chiara, et al.
Incidence of increased 68
Ga-DOTANOC uptake in the
pancreatic head in a large series of extrapancreatic NET
patients studied with sequential PET/CT. J Nucl Med.
2011;52(6):886e890.
Fig. 4 e Surgical specimen reveals the mass (M), distal
pancreas (P), Duodenum (D), Proximal jejunum (J) and
spleen (Sp).
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