Which pair of markers best indicates epithelial origin in a tumor immunoprofile?

• A. S100 & HMB45
• B. Glypican 3 & CD30
• C. CK18 & EMA
• D. CD56 & INSM1

Answer: (C)

Epithelial tumors show markers that come from the epithelial lineage. Cytokeratin 18 is a type of cytokeratin found in many simple epithelia, and epithelial membrane antigen (EMA) is a membrane-associated glycoprotein widely present on epithelial cells. When a tumor tests positive for both CK18 and EMA, it strongly supports epithelial differentiation because these markers together are characteristic of epithelial origin, helping distinguish it from non-epithelial lineages.

Other marker pairs point to different origins: S100 and HMB45 suggest melanocytic or neural crest lineage; Glypican 3 and CD30 are associated with certain embryonal/germ cell or hepatocellular contexts; CD56 and INSM1 indicate neuroendocrine differentiation.