The study is a feasibility and validation study of the sentinel lymph node (SLN) procedure in all stages of colon cancer. If the SLN can be reliably identified, it could be submitted to a more accurate histopathological examination (multiple sections, special staining). The detection of micrometastases in the SLN (occult stage III, upstaging) is possible. Patients with micrometastases should be considered at higher risk.

Additionally, a search for occult metastatic tumor cells in the bone marrow is performed.

Inclusion Criteria:

• Colon cancer at any stage diagnosed histologically or high degree of suspicion for colon cancer at endoscopy, which cannot be confirmed with certainty in the biopsy. The diagnosis of cancer must be certain in the definitive histology.
• Possibility of transabdominal injection of the dye (cancers below the peritoneal reflection in which the injection of dye must be carried out through rectoscopy, are therefore excluded).
• Patient's informed consent

Exclusion Criteria:

• Prior intrabdominal tumor surgery
• Other preexisting malignancies
• Hypersensitivity/allergy to dye (isosulfan blue)
• Pregnancy
• Breast-feeding
• No patient's informed consent