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Carbonic anhydrase IX

Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 27 February 2012, last major update February 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● 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 Feb 14 [Epub ahead of print])
● 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

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

Papillary renal cell carcinoma shows focal expression

Rectal cancer

Positive staining - disease

● Clear cell renal cell carcinoma (diffuse, membranous expression, Am J Surg Pathol 2011;35:949, Am J Surg Pathol 2008;32:377, low grade > high grade, Am J Clin Pathol 2010;134:873), clear cell papillary renal cell carcinoma
● Renal urothelial carcinoma (90%), papillary renal cell carcinoma (57%), renal tumors with Xp11.2 translocation (40%) (Am J Surg Pathol 2009;33:241)
● Most carcinomas of breast, cervix, endometrium, lung, liver, stomach; also brain tumors, neuroendocrine tumors, mesotheliomas (Am J Pathol 2001;158:905)
● Variable adrenal cortical and germ cell tumors (Histopathology 2011;59:1229)

Negative staining

● Kidney (normal); chromophobe renal cell carcinoma on renal oncocytoma

End of Stains > Carbonic anhydrase IX

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