CK7 negative and CK20 negative immunostaining favors which organ systems?

• A. Biliary tract, pancreas, stomach
• B. Brain, spinal cord
• C. Liver, kidney, prostate
• D. Colon, rectum, stomach

Answer: (C)

CK7 and CK20 patterns help identify where a tumor might have originated. CK7 is often present in tumors from the lung, breast, pancreas, biliary tract, and related sites, while CK20 is common in colorectal and some urothelial tumors. When a tumor is negative for both CK7 and CK20, it points toward tissues that do not express these keratins, with liver, kidney, and prostate being classic examples. Among the given options, liver, kidney, and prostate fit this CK7-/CK20- profile best, whereas colon/rectum/stomach typically show CK20 positivity or CK7 expression, and brain/spinal cord tumors are not usually categorized this way. Thus, CK7 negative and CK20 negative immunostaining favors liver, kidney, and prostate.