This is an open-label study in adults to determine feasibility of using CYTALUX™ (pafolacianine) injection with near-infrared (NIR) fluorescent imaging for detecting any type adenocarcinoma (gastric, esophageal and appendiceal).

Inclusion Criteria:

1. Patients 18 years of age and older of any sex.
2. Have a primary diagnosis, or a high clinical suspicion, of gastroesophageal adenocarcinoma based on CT (computed tomography)/PET (positron emission tomography) or other imaging (Cohort 1) or diagnosis of appendiceal adenocarcinoma with a high clinical suspicion of peritoneal carcinomatosis (Cohort 2).
3. Have an indication for surgical intervention for gastroesophageal tumor resection or diagnostic laparoscopy for assessment of peritoneal disease burden.
4. Willingness to stop the use of folate, folic acid, or folate-containing supplements within 48 hours before administration of CYTALUX.
5. Willingness of research participant to give written informed consent.

Exclusion Criteria:

1. Any medical condition that in the opinion of the investigators could potentially jeopardize the safety of the subject.
2. History of anaphylactic reactions to products containing indocyanine green for near infrared imaging. Subjects with a medical history of 'idiopathic anaphylaxis' will require evaluation.
3. History of allergy to any of the components of CYTALUX™ (pafolacianine) injection.
4. Presence of any psychological, familial, sociological condition or geographical challenges potentially hampering compliance with the study protocol or follow-up schedule.
5. Known sensitivity to fluorescent light.
6. Women of childbearing potential who are pregnant or plan to become pregnant during the study.