Alternate Test Names:
Cytokeratin 20; CK20

Methodology: IHC

Clinical Significance:
Identifies a subset of carcinomas. Co-analysis of expression of cytokeratin 7 can be helpful in the identification of the primary site of carcinomas presenting at metastatic sites. CK20 is also a marker of Merkel cell tumors, usually displaying a dot-like perinuclear pattern of expression.

Subcellular Localization: Cytoplasmic

Organ: Colon & Other GI

Disease State: Carcinomas of Unknown Primary

CPT Code(s): 88342 or 88341 (reference only; CPTs may vary)

Turnaround Time: Within 1-2 business days of receipt

Schedule: Monday - Friday

Specimen Requirements:
• Formalin-fixed, paraffin-embedded (FFPE) tissue block or cell block - OR -
• 1 unstained slide for each test requested plus 3-4 additional unstained slides cut at 4µm