• All IHC stains will include a positive control tissue

• 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 neuroblastomas have also been shown to express PAX5

Submit a formalin-fixed, paraffin embedded tissue block

Formalin-fixed, paraffin embedded (FFPE) tissue block

FFPE tissue section mounted on a charged, unstained slide

Ambient (preferred)

• Unlabeled/mislabeled block
• Insufficient tissue
• Slides broken beyond repair

Immunohistochemical staining and microscopic examination

If requested, an interpretive report will be provided

Specifications

• 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

References

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.