Metastatic small bowel neuroendocrine tumor

Case contributed by Matthew Tse
Diagnosis certain

Presentation

Colonoscopy for constipation. Very inflamed ileocecal valve. Unable to get into terminal ileum itself. Evidence of small bowel Crohn's?

Patient Data

Age: 60 years
Gender: Female

Enterography

ct

There is a lesion at the ileocecal valve which shows marked uniform enhancement measuring approximately 3cm. No upstream dilatation to suggest obstruction. There is submucosal enhancement of a short section of distal ileum leading up to this suggestive of engorged vessels.

There is nodularity along the draining ileocolic vessels and mild surrounding stranding.

Grossly normal appearances of the remainder of the large and small bowel.

There is a low density lesion within segment 6 of the liver with peripheral nodular enhancement in keeping with a benign hemangioma.

Well-defined foci of hypoattenuation in the right lobe of the liver in keeping with benign lesions e.g. cysts. Remainder of the liver is normal.

Normal gallbladder, adrenals, kidneys, pancreas and spleen.

No free abdominal or pelvic fluid.

Imaged lung bases are clear.

No destructive bone abnormality.

Opinion:

Enhancing lesion at the terminal ileum with draining mesenteric nodal mass suspicious of a neuroendocrine tumor.

Octreotide scan

Nuclear medicine

Selected image from Nuclear Medicine Octreotide Scan.

Planar imaging demonstrates focal tracer uptake in the right lower abdominal quadrant similar to, if not greater than, the background spleen (Krenning 3/4). On the subsequent SPECT-CT acquisition this localizes to the soft tissue lesion at the terminal ileum and ileocecal valve. The 9 mm short axis ileocolic lymphadenopathy is not Octreotide-avid but may to be too small to resolve with SPECT.

Liver with Gadovist

mri

There are four small lesions characteristics concerning for metastases (hypervascular, faint washout, diffusion restriction):

Lesion 1 - at the border of segments 6/7

Lesion 2 - subcapsular segment 5

Lesion 3 - small lesion peripherally in segment 6 (superior to the hemangioma)

Lesion 4 - just medial to middle hepatic vein (segment 4), slightly more equivocal with no DWI.

Elsewhere, there are several hemangiomas (largest 20mm subcapsular segment 6) along with a cyst in segment 5 and some perfusional change adjacent to the GB fossa.

Patent portal vein. No biliary dilatation. No significant extrahepatic pathology evident.

Conclusion: Four small liver lesions are atypical for hemangiomas, and concerning for metastases as described.

Liver (select images)

mri

Selected images from the MRI. Lesions 1-3 all demonstrated ill-defined high T2 signal with arteirial hyperenhancement which becomes iso- or hypo-intense to background liver on portal venous phase with corresponding diffusion restriction.

Lesion 4 is more equivocal, given that there is some apparent retained Gadovist concentration in the delayed phase sequence and no convincing low signal on ADC to suggest diffusion restriction.

Case Discussion

The avid enhancement of the terminal ileum initially caused confusion with a possible arteriovenous malformation (AVM) being considered however this area was biopsied on colonoscopy prior to the CT examination and it was reasoned that the lack of brisk bleeding after sampling made AVM less likely. The presence of a mesenteric soft tissue mass with apparent indrawing of the surrounding vessels also supported the differential of neuroendocrine tumor.

Following confirmation of avidity on Octreotide scan and absence of any distant avid disease the patient proceeded to right hemicolectomy. Histology and immunohistochemistry confirmed a well-differentiated neuroendocrine tumor breaching the serosal surface, with a mesenteric tumor deposit and 10/17 involved draining nodes (including the highest sampled node) giving a pathological staging of pT4 pN1 R0 resection. Vascular and perineural invasion was also present on histology.

The MRI liver was performed some 5 months after the CT enterography (3 months post-surgery) to ensure the liver lesions on CT were indeed benign. The hypoattenuating foci on CT did correspond with benign entities, though the MRI did demonstrate suspicious lesions as described above. A subsequent gallium-68 DOTATATE nuclear medicine scan (imaging not shown here) showed avidity in the two largest lesions which were described on MRI, it was felt the third lesion was too small to have demonstrated avidity and is still suspicious of a metastasis.

At present the patient is under clinical follow up with plan for repeat MRI liver in the near future at the time of writing.

Acknowledgements to Dr Rachel Allard, Dr Adam Laverty and Dr Hssein Al-Chalabi.

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