Observational Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Sep 14, 2015; 21(34): 10008-10017
Published online Sep 14, 2015. doi: 10.3748/wjg.v21.i34.10008
Computed tomography and magnetic resonance imaging features of lipid-rich neuroendocrine tumors of the pancreas
Yoshihiko Fukukura, Toshikazu Shindo, Michiyo Higashi, Koji Takumi, Tomokazu Umanodan, Tomohide Yoneyama, Takashi Yoshiura
Yoshihiko Fukukura, Toshikazu Shindo, Koji Takumi, Tomokazu Umanodan, Tomohide Yoneyama, Takashi Yoshiura, Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima City 890-8544, Japan
Michiyo Higashi, Department of Human Pathology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima City 890-8544, Japan
Author contributions: Fukukura Y designed the research and wrote the paper; Shindo T, Takumi K, Umanodan T, Yoneyama T and Higashi M analyzed and interpreted the data; Yoshiura T revised the article critically for important intellectual content; all authors participated in drafting or revising the article, and approved the submitted manuscript.
Institutional review board statement: This study was institutionally approved by Kagoshima University Graduate School of Medical and Dental Sciences.
Informed consent statement: The institutional review board did not require informed consent for a retrospective study using medical records or imaging examinations.
Conflict-of-interest statement: There are no competing interests to disclose in relation to this study.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Yoshihiko Fukukura, MD, PhD, Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City 890-8544, Japan. fukukura@m.kufm.kagoshima-u.ac.jp
Telephone: +81-99-2755417 Fax: +81-99-2651106
Received: March 19, 2015
Peer-review started: March 25, 2015
First decision: April 13, 2015
Revised: April 26, 2015
Accepted: July 15, 2015
Article in press: July 15, 2015
Published online: September 14, 2015
Processing time: 179 Days and 2.5 Hours
Abstract

AIM: To clarify the computed tomography (CT) and magnetic resonance imaging (MRI) characteristics of lipid-rich pancreatic neuroendocrine tumors (PanNETs).

METHODS: Enhanced CT and MRI performed before pancreatectomy in 29 patients with 34 histologically-confirmed PanNETs was retrospectively reviewed. Tumor attenuation on CT and signal intensities on conventional (T1- and T2-weighted) and chemical shift MRI were qualitatively analyzed and compared alongside adipose differentiation-related protein (ADRP) immunostaining (ADRP-positive: lipid-rich; ADRP-negative: non-lipid-rich) results using Fisher’s exact test or the Mann-Whitney U test. Signal intensity index on chemical shift MRI was quantitatively assessed.

RESULTS: There were 15 lipid-rich PanNETs (44.1%) in 12 patients (41.4%). Tumor attenuation during the early, portal venous, and delayed phases of enhanced CT (P = 0.888, 0.443, and 0.359, respectively) and signal intensities on conventional MRI (P = 0.698 and 0.798, respectively) were not significantly different between lipid-rich and non-lipid-rich PanNETs. Four of the 15 lipid-rich PanNETs exhibited high signal intensity on subtraction chemical shift MRI, and the association of high signal intensity on subtraction imaging with lipid-rich PanNETs was significant (4 of 15 lipid-rich PanNETs, 26.73%, vs 0 of 19 non-lipid-rich PanNETs, 0%, P = 0.029). Lipid-rich PanNETs showed a significantly higher signal intensity index than non-lipid-rich PanNETs (0.6% ± 14.1% vs -10.4% ± 14.4%, P = 0.004). Eight of 15 lipid-rich PanNETs, vs 0 of 19 non-lipid-rich PanNETs, had positive signal intensity index values in concordance with lipid contents.

CONCLUSION: CT contrast enhancement and conventional MR signal intensities are similar in lipid-rich and non-lipid-rich PanNETs. Chemical shift MRI can demonstrate cytoplasmic lipids in PanNETs.

Keywords: Neoplasms; Chemical shift magnetic resonance imaging; Pancreas; Computed tomography; Neuroendocrine tumors

Core tip: Little is known about lipid-rich pancreatic neuroendocrine tumors (PanNETs). In the current study, we clarify computed tomography (CT) and magnetic resonance imaging (MRI) characteristics of lipid-rich PanNETs. Adipose differentiation-related protein antibody positive lipid-rich cells were observed in 15 of 34 tumors (44.1%). Lipid-rich PanNETs had a similar appearance to usual PanNETs on enhanced CT. On chemical shift MRI, positive signal intensity index values in concordance with lipid contents were observed in eight of 34 tumors (23.5%). Lipid-rich PanNETs should be included in differential diagnosis whenever chemical shift MRI demonstrates lipid components within hypervascular pancreatic tumors.