Carbonic anhydrase IX

Author: Nat Pernick, M.D. (see Authors page)

Revised: 10 November 2015, last major update February 2012

Copyright: (c) 2003-2015,, Inc.

PubMed Search: carbonic anhydrase ix
Definition / General
  • Also called CAIX
  • Hypoxia induced protein expressed in some renal tumors
  • Transmembrane enzyme that regulates cell proliferation, adhesion, invasion
Clinical Features
  • May predict doxorubicin resistance in early-stage breast cancer (Br J Cancer 2012;106:916)
  • Deficiency of carbonic anhydrase II, required by osteoclasts and renal tubular cells to excrete hydrogen ion, can cause osteopetrosis
Uses by Pathologists
  • Marker of clear cell renal cell carcinoma
  • Differentiate metastatic clear cell renal cell carcinoma (positive) from thyroid tumors (Am J Surg Pathol 2011;35:757)
Micro Images

Images hosted on other servers:

Clear cell renal cell carcinoma: low grade (left) versus high grade (right)

Papillary renal cell carcinoma shows focal expression

Rectal cancer

Positive Staining - Disease
Negative Staining
  • Kidney (normal); chromophobe renal cell carcinoma on renal oncocytoma