Mesenteric plexiform neurofibroma

Case contributed by Maria Virginia Dalmasso
Diagnosis almost certain

Presentation

Palpable abdominal mass, constipation and abdominal pain.

Patient Data

Age: 7 years old

Ultrasound mesogastrium

ultrasound

Multiple mesogastric hypoechoic nodules with hyperechoic background and several feeding vessels.

Large lobulated mass extending from the left lateral aortic region to the pelvis reaching the pouch of Douglas and the prevesical region Its located below the colonic frame and displaces superior and laterally some small bowel loops. It shows heterogeneous signal intensity, predominantly hyperintense in T2 and STIR sequences with hypointense center ("ring pattern") and iso-hypointense in T1 sequences. Mild central enhancement in late phases is seen.

Case Discussion

Plexiform neurofibroma is a benign proliferation of peripheral nerves, pathognomonic of neurofibromatosis type 1 (NF1), of which this patient had a history. 

It affects neural plexuses and multiple medium or/and large caliber branches of nerves, generating large fusiform and tortuous masses.

It can be seen in 16-40% of patients with NF1 affecting any organ. However, intra-abdominal or retroperitoneal localization is very rare.

MRI typical findings include hypointense T1 structures; in T2-weighted images ring-like structures with high T2 signal in the periphery correspond to myxoid matrix, and low central T2 signal represents collagen and fibrous tissue (target-sign). The areas of low T2 signal have mild enhancement following gadolinium administration.

MRI is the best choice for the medical study and follow-up of neurofibromas since they can become malignant in 2-5% of cases. This fact should be suspected when persistent pain, increasing mass size and border irregularity are present.

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