Table 1_Peritoneal neuroendocrine carcinoma of unknown primary with markedly elevated alpha-fetoprotein: a case report.docx

Liver enhanced magnetic resonance imaging and gastrointestinal endoscopy did not reveal any space-occupying lesions, while abdominal puncture did not detect tumor cells. The patient’s whole-body PET-CT revealed extensive peritoneal thickening and increased FDG metabolism. Subsequent laparoscopic exploration revealed numerous nodules and masses of varying sizes with a firm texture in the greater omentum, small intestine surface, mesentery, and parietal peritoneum.

Immunohistochemistry of the omentum demonstrated positive results for AE1/AE3, Syn, CgA, and AFP, leading to a final diagnosis of large cell NEC of unknown primary, with a presumed primary peritoneal origin. Due to the presence of multiple peritoneal nodules, radical surgery was not feasible, and EP combined with camrelizumab was initiated. AFP levels showed an overall progressive increase, peaking at 5315 ng/mL on May 25, with a slight subsequent decline to 4948.4 ng/mL on June 20.

Unfortunately, the patient discontinued chemotherapy after two cycles due to severe nausea and vomiting; he subsequently succumbed to the disease.</p>Conclusions<p>We propose the hypothesis that dynamic changes in AFP levels could reflect tumor burden and treatment response in a subset of AFP-producing NECs. However, this hypothesis requires validation in larger cohort studies. It is also important to distinguish its potential role as a monitoring biomarker from an established prognostic biomarker.</p>