Discussion

Primary mesenteric NETs, defined as neuroendocrine neoplasms arising within the mesentery without a discernible gastrointestinal, pancreatic, or other primary site, are among the rarest variants of NETs [2]. The majority of mesenteric NETs encountered in clinical practice represent metastatic deposits from ileal NETs, which characteristically produce a desmoplastic reaction in the mesentery [4]. Distinguishing a true primary mesenteric NET from mesenteric metastasis of a small, occult ileal primary is therefore a significant diagnostic challenge.

In the present case, thorough intraoperative exploration, including examination of the entire length of the small and large bowel, stomach, liver, and pancreas, identified no additional lesions. The CECT findings of a stalk connecting the mass to the terminal ileum raised the possibility of an ileal primary; however, no mucosal or intramural ileal lesion was identified. The absence of a primary bowel lesion, along with the isolated mesenteric location, supports the diagnosis of a primary mesenteric NET in this case, though definitive exclusion of a small occult primary requires thorough pathological sampling.

The postoperative hypertension observed in this patient is a recognized, albeit rare, complication following resection of functioning NETs, attributed to catecholamine release, serotonin excess, or rebound vasoconstriction following removal of a vasodilatory tumor [5]. The presence of lymphovascular emboli in a WHO Grade I tumor warrants careful postoperative surveillance despite the low-grade histology.

Complete surgical resection with tumor-free margins, as achieved in this case, is the mainstay of curative treatment for localized mesenteric NETs. Postoperative functional imaging with somatostatin receptor scintigraphy or ⁶⁸Ga-DOTATATE-peptide PET-CT is essential for staging, detection of occult primaries, and surveillance for recurrence [6].