Allina Health Laboratory a part of Abbott Northwestern Hospital



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Test Name:PAX5 by IHC
Test Number:12376 - Technical only; 12379 - Technical & Interpretation
Collect:Formalin-fixed, paraffin embedded (FFPE) tissue block
Container:FFPE tissue block
Processing:Submit processed tissue block or tissue section mounted on a charged, unstained slideSubmit processed tissue block
Transport/Stability:Ambient (preferred)
Alternate Names:B-cell lineage-specific activator protein
Performing Lab:AHL - Immunohistochemistry
Days Set Up:Mo - Fr
Expected TAT:1 - 2 days
Ref. Ranges:If requested, an interpretive report will be provided
All IHC stains will include a positive control tissue
Processing Details:

  • PAX5, is a transcription factor that is necessary for B-lineage commitment and development
  • PAX5 exceeds the specificity and sensitivity of CD20, because of its earlier expression in B-cell differentiation and its ability to detect all committed B cells (until the plasma cell stage where it will be negative)
  • Virtually B-cell specific

Staining pattern:
  • Nuclear
  • Intended for the identification of cells of B-cell lineage (reacts with 94 to 100% of B-cell neoplasms); diffuse large B-cell lymphomas not expressing Pax5 are usually those with terminal B-cell differentiation
  • PAX5 has been reported to stain Reed-Sternberg cells in 97% of classic Hodgkin lymphomas
  • PAX5 is a more specific marker than CD79a for B-cell ALL, and will also react with t(8;21) AML (due to aberrant expression of B-cell genes)
  • Multiple myelomas and normal plasma cells will usually show no staining; PAX5 will stain rare cases of CD20-positive multiple myeloma
  • PAX5 will also stain neuroendocrine carcinomas, such as Merkel cell carcinoma (93%) and small cell carcinoma (73%); no carcinoid tumors show staining according to one report; some neuorblastomas have also been shown to express PAX5
  1. Torlakovic E, et al: The value of anti-pax5 immunostaining in routinely fixed and paraffin-embedded sections: a novel pan pre-B and B-cell marker. Am J Surg Pathol. 2002 Oct;26(10):1343-50.
  2. Dong HY et al: B-cell specific activation protein encoded by the Pax5 gene is commonly expressed in merkel cell carcinoma and small cell carcinoma. Am J Surg Pathol. 2005 May;29(5): 687-92.
  3. Robichaud GA et al: Human Pax5 C-terminal isoforms possess distinct transactivation properties and are differentially modulated in normal and malignant B cells. J Biol Chem. 2004 Nov 25;279(48):49956-63.
  4. Tiacci E et al: Pax5 expression in acute leukemias: higher B-lineage specificity than CD79a and selective association with t(8;21)-acute myelogenous leukemia. Cancer Res 2004 Oct 15;64(20):7399-404.
  5. Lin P et al: Expression of Pax5 in CD20-positive multiple myeloma assessed by immunohistochemistry and oligonucleotide microarray. Mod Pathol 2004 Oct;17(1): 1217-22.
  6. Feldman AL et al: Diagnostic uses of Pax5 immunohistochemistry. Adv Anat Pathol 2007;14:323-334.
Method:Immunohistochemical staining
Microscopic examination
CPT Codes:88342 - 1st stain
88341 - each additional stain
Date Created:08/07/2017
Revised Date:10/19/2018