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Comparative Study
. 2017 Feb;72(2):150-158.
doi: 10.1016/j.crad.2016.10.021. Epub 2016 Nov 24.

Contrast-enhanced MDCT in patients with pancreatic neuroendocrine tumours: correlation with histological findings and diagnostic performance in differentiation between tumour grades

E Belousova  1 , G Karmazanovsky  2 , A Kriger  3 , D Kalinin  4 , L Mannelli  5 , A Glotov  4 , N Karelskaya  6 , O Paklina  7 , A Kaldarov  3
Affiliations
Comparative Study

Contrast-enhanced MDCT in patients with pancreatic neuroendocrine tumours: correlation with histological findings and diagnostic performance in differentiation between tumour grades

E Belousova et al. Clin Radiol. 2017 Feb.

Abstract

Aim: To identify the multidetector computed tomography (MDCT) features of pancreatic neuroendocrine tumours (pNETs), which correlate with tumour histology and enable preoperative grading.

Materials and methods: Thirty-nine patients with histologically confirmed pNET who underwent preoperative contrast-enhanced MDCT were included in this study. Nineteen tumours were classified as Grade 1 (G1) and 20 as Grade 2 (G2). Histopathology slides were reviewed to assess the intratumoural microvascular density (MVD) and the amount of tumour stroma. Computed tomography (CT) image analysis included tumour size, margin delineation, calcifications, homogeneity, contrast enhancement (CE) pattern, tumour absolute and relative enhancement, presence of cystic changes, pancreatic duct dilatation, regional and distant metastases. The diagnostic ability to predict tumour grade was measured for each MDCT finding and their combinations.

Results: The mean arterial enhancement ratio had a mean±standard deviation of 1.53±0.45 in G1 and 1.01±0.33 in G2 pNETs (p=0.0003) and correlated with intratumoural microvascular density (MVD; r=0.55, p=0.0002). Tissue stroma percentage did not correlate with imaging findings. Late CE of the tumour (the peak attenuation observed in the venous phase) was significantly associated with G2. Tumour size >20 mm, arterial enhancement ratio <1.1, and late CE showed 74.4%, 79.5%, and 74.4% accuracy, respectively, in diagnosing G2 tumours, while the accuracy of at least two of these criteria used in combination was 82%. Based on these results, a diagnostic algorithm was proposed, which showed high interobserver agreement (k=0.82) in the prediction of tumour grade.

Conclusion: Contrast-enhanced MDCT features correlate with histological findings and enable the differentiation between G1 and G2 pNETs during preoperative examination.

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Figures

Figure 1
Figure 1
Box-and-whisker plots of the relative enhancement ratios in G1 and G2 pNETs, evaluated in the arterial, venous, and delayed phases. The enhancement ratios show a statistical difference between grades in the arterial (p=0.0003) and venous (p=0.01) phases.
Figure 2
Figure 2
The relative arterial enhancement ratio in correlation with intratumoural MVD (r=0.55, p=0.0005)
Figure 3
Figure 3
CT post-contrast appearance of a G1 pNET: a small lesion in the pancreatic head (yellow arrow) shows early enhancement during the arterial phase (a) with wash-out in the venous (b) and delayed (c) phases (type A CE pattern). The lesion has an arterial enhancement ratio of >1.1. (d) Immunostaining with CD34 antibody (×200) highlights vessels (red), showing that the intratumoural MVD is high (14%)
Figure 4
Figure 4
CT post-contrast appearance of a G2 pNET: a lesion in the pancreatic body (yellow arrow) shows hypoattenuation in the arterial phase (a) and hyperattenuation in the venous (b) and delayed (c) phases (type B CE pattern). The lesion has an arterial enhancement ratio of <1.1. Note the metastatic lesion (red arrow) in the right liver lobe with peripheral rim enhancement. (d) Immunostaining with CD34 antibody highlights vessels (red), showing that the intratumoural MVD is low (4%).
Figure 5
Figure 5
The diagnostic algorithm for differentiation between G1 and G2 pNETs.
See this image and copyright information in PMC

References

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