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Medical School, University of Crete 71110, Heraklion, Crete, Greece
Hough et al. [1] in their very interesting article have described the "teardrop superior mesenteric vein" as a new sign for pancreatic cancer unresectability on CT examinations. The authors found that this sign, added to the already established CT criteria [2, 3], significantly increases the sensitivity and accuracy of CT for resectability of pancreatic head tumors [1].
We retrospectively reviewed the MR examinations of 18 consecutive patients with proven pancreatic cancer in respect to superior mesenteric vein changes in shape. Two patients had a resectable tumor in the head of the pancreas and underwent a successful pancreatoduodenectomy. Sixteen patients had an unresectable disease (13 in the head, two in the body, and one in the tail of the pancreas); 14 were operated on, and two did not have any surgical exploration or surgical palliative treatment. In seven patients with unresectable disease, the mass was in contiguity with the superior mesenteric vein that exhibited occlusion or reduction in caliber.
Superior mesenteric vein deformity was observed in seven other patients with unresectable disease in the head (n = 6) or the tail (n = 1) of the pancreas (Fig. 2). On axial MR images, the superior mesenteric vein had a teardrop shape in three cases, a linear configuration in two, and a triangular appearance in two (Fig. 3). Normal shape of the superior mesenteric vein was seen in four patients, two with resectable disease in the head of the pancreas and two with unresectable disease originating from the body. The superior mesenteric vein deformities were best seen on 4-mm T1-weighted images with fat saturation immediately after gadolinium (0.2 mg/kg) IV bolus injection.
The teardrop superior mesenteric sign, initially described as a CT sign of pancreatic cancer unresectability [1], can also be observed on axial MR images. It may not be exclusively observed in patients with unresectable neoplasms in the head of the pancreas, as reported by Hough et al. [1]. In addition to the teardrop or linear configuration [1], a triangular superior mesenteric vein shape can also be seen.
Superior mesenteric vein deformity, in the absence of encasement or thrombosis, may be considered as a useful MR imaging sign of pancreatic cancer unresectability alone or in combination with other findings.
References
Beth Israel Deaconess Medical Center Harvard Medical School Boston, MA 02215
We thank Dr. Prassopoulos and his colleagues for expanding the "teardrop" superior mesenteric vein sign of pancreatic cancer unresectability from CT to MR imaging. This strengthens the original CT observation [1]. Confirmation by another modality validates the sign and makes the possibility of it being an artifact less likely. As seen on CT, and now on MR imaging, change in the shape of the superior mesenteric vein is an important indicator of tumor unresectability. However, caution should be exercised when, in addition to tumor, this is the only other abnormal finding. In such a situation, calling a tumor unresectable in essence denies the only possibility for cure of pancreatic adenocarcinoma. The mere change in shape (flattening) of one side or smooth displacement of the superior mesenteric vein on axial images is not an absolute CT sign of unresectability. At least half of these patients can undergo radical pancreatoduodenectomy [2, 3]. At least two thirds of the vein perimeter needs to be involved, as seen in the teardrop superior mesenteric vein. Prassopoulos et al. nicely show that in addition to teardrop, the same mechanism can alter the cross-sectional shape of the superior mesenteric vein into linear (oval?) or triangular appearance (Figs. 2 and 3). The presumed underlying cause of change in shape of the vein is either direct tumor infiltration or peritumoral fibrosis that retracts or tethers the vessel. It would be important if MR imaging could distinguish between the two conditions.
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