The role of 68Ga-DOTATATE PET/CT in extensive IgG4-positive fibrosis surrounding a mesenteric lymph node metastasis of a neuroendocrine tumor: A case report

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Introduction: IgG4 expression is commonly seen in mesenteric tumor deposits from small intestine neuroendocrine tumors leading to a dense fibrotic response which can simulate IgG4-related sclerosing mesenteritis in medical images, hereby impeding a correct diagnosis.

Aim(s): To report a case where 68Ga-DOTATATE PET/CT had an important role in discriminating between IgG4 fibrosis and NET lymph node metastasis.

Materials and methods: A 56-year-old female presented with right iliac fossa pain. Abdominal CT showed a soft-tissue mesenteric mass in the right iliac fossa, suggestive of sarcoma. The mass was located adjacent to the vena cava inferior (VCI) and the right ureter, compromising urinary flow. Ureterorenoscopy followed promptly, excluding ureteral invasion and a DJ stent was placed in the right ureter. Abdominal MRI scan could not show proper delineation of the mass with the wall of the VCI and invasion was not ruled out, hence hampering the probability of an R0 resection. Biopsy of the mass was performed via retroperitoneal puncture, revealing a well-differentiated NET (Ki-67 index 2%). 68Ga-DOTATATE PET/CT revealed two NETs with strong SSTR expression in the terminal ileum. In addition, the mesenteric mass showed strong SSTR expression in a small, central area only, with the vast majority of this mesenterial mass showing absent 68Ga-DOTATATE uptake.

Conference: 18th Annual ENETS Concerence (2021)

Presenting Author:

Authors: Ahmadi Bidakhvidi N, Cuyle P, Sagaert X, Ballaux F, De Bruecker Y,

Keywords: small intestine neuroendocrine tumor, 68Ga-DOTATATE PET/CT, mesenterial lymph node, fibrosis, IgG4,