Malignant Triton Tumor of the Ileocolic Mesentery with Neurofibromatosis Type 1: A Case Report and Literature Review.

Malignant triton tumors (MTTs) are rare tumors histologically defined as malignant peripheral nerve sheath tumors with additional rhabdomyoblastic differentiation. MTTs occur more frequently in patients with neurofibromatosis type 1 (NF1). MTTs are most commonly found in the extremities, head and neck, and trunk; however, no cases in the mesentery have been reported. In this report, we describe a case of primary MTT of the mesentery in a patient with NF1. A 29-year-old woman with NF1 visited a clinic for abdominal pain and was referred to our hospital for treatment of an abdominal tumor detected by CT. Contrast-enhanced CT showed a 20-cm irregular mass on the right side of the abdominal cavity. The mass was extensively bordered by the superior mesenteric vein (SMV), but there was no obvious distant metastasis. The patient was diagnosed with a mesenteric tumor with SMV invasion. An open biopsy was performed, and the histopathological diagnosis was MTT. The patient was discharged on the 11th day after surgery but returned to our hospital on the 17th day due to abdominal pain. The tumor had markedly enlarged on CT, and a semi-emergent tumor resection was performed. An enlarged mass was detected, but no peritoneal dissemination was observed. The tumor was in extensive contact with the SMV, but it could be dissected. A right hemicolectomy was performed, and the tumor was removed. Histopathological findings revealed a 26.5 × 17.5 × 9.5 cm tumor in the ileocolic mesentery. The dissected surface was negative for margins, with no exposed tumors. The histopathological diagnosis was MTT. Follow-up CT on postoperative day 14 revealed multiple peritoneal nodules. The patient was diagnosed with recurrent peritoneal dissemination and treated with two courses of doxorubicin and one course of pazopanib. However, she died 5 months postoperatively due to worsening peritonitis carcinomatosis. We present a case of primary MTT of the mesentery. Our findings suggest that biopsy may lead to peritoneal dissemination. In patients with suspected MTT, such as those with NF1, abdominal cavity biopsy should be avoided, and diagnostic treatment should prioritize surgical resection.