Malignant gastrointestinal neuroectodermal tumor: A rare differential diagnosis of neuroendocrine neoplasm of the Small Intestine - Case reports and Review of the literature

The malignant gastrointestinal neuroectodermal tumor (GNET) is a rare and very aggressive neoplasm. Due to its rarity, the tumor is often misdiagnosed. We report on two female patients who were operated on under the suspected diagnosis of a neuroendocrine tumor of the small intestine (SI-NET). The patients, aged 37 and 57 years, presented with symptoms of bowel obstruction. In a 37-year-old patient with a chronic bowel obstruction, MRI enterography revealed a tumor in the jejunum with lymph node metastases as well as liver metastases. Laparotomy confirmed the presence of a tumor in the jejunum with lymph node and liver metastases. Segmental resection of the small bowel with lymphadenectomy was performed. The remaining hepatic metastases in the right liver lobe were removed 8 weeks later by right hemihepatectomy. Four months later, the Ga68-FAPI-PET/CT showed significant disease progression. Unfortunately, the patient died 22 months later after initial diagnosis. In the second case, a 57-year-old female presented to our clinic with progressive bowel obstruction for 2 years. The MRI examination revealed a small bowel obstruction due to a tumor mass in the ileum with lymph node metastases suspicious for a SI-NET. Exploratory laparotomy revealed a tumor in the jejunum with peritoneal metastases. A vessel-sparing small bowel resection with lymphadenectomy and partial peritonectomy was performed. The follow-up examinations using MRI and CT six months postoperatively showed no evidence of tumor progression. The final pathology confirmed the diagnosis of a GNET in both cases. Molecular analysis revealed EWSR1 translocations in the tumors of both patients.