p40 is a member of the p53 family, and is an isoform of p63.  It is also known as delta-Np63.  p63 can have different isoforms, and p40 reacts with truncated dominant isoforms of the p63 gene. (Brown, et. al.; Bishop, et. al.; and Ross, et. al.)  p40 performs in a similar fashion to p63, but with so-called better specificity. (Bishop)

 

p40 appears very sensitive for lung squamous cell carcinomas (>90%) and urothelial carcinomas (>88%) from multiple studies. (Gaily, et. al. and Bishop, et. al.)  Rarely (<5%) breast, biliary tract/pancreas, endometrium, and prostate showed reactivity, and evaluation of multiple cases (40-100 each) of renal cell carcinoma, thyroid, hempatocellular carcinoma, colon adenocarcinoma, stomach adenocarcinoma, and ovarian epithelium failed to show any reactivity (negative). (Brown, et. al.)

 

Ross, et. al. claims superiority of p40 over p63 because only 3% of lung adenocarcinomas showed any positivity with p40 compared to 31% with p63.  To the inexperienced pathologist using p63 in lung cancer subcategorization, partial positivity with p63 may lead to comments like “focal squamous differentiation” or “cannot exclude a component of squamous cell carcinoma”.  These comments should be avoided, if possible.  Often oncologists will not give the patient Avastin, which is an important therapy option, if there is any evidence of squamous differentiation due to the risk of pulmonary hemorrhage.

 

Where some pathologists find variable subset nuclear expression with p63 in lung adenocarcinomas, others find such expression pattern as re-inforcing support for the diagnosis of lung adenocarcinoma.  It is important to remember a basic tenant (general rule) in interpreting nuclear transcription markers like p40 and p63; expression should be consistent and diffuse for the tumor cells of interest.  If expression does not meet this threshold, then one may be wise to consider additional markers in a panel to confirm differentiation.   Pathologists must NOT think of stains as positive and negative, but in the context of the pattern of expression, and what that means.

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References:

Brown AF, Sirohi D, Fukuoka J, Cagle PT, Policarpio-Nicolas M, et al. (2013) Tissue-preserving antibody cocktails to differentiate primary squamous cell carcinoma, adenocarcinoma, and small cell carcinoma of lung. Arch Pathol Lab Med 137: 1274–1281. doi:10.5858/arpa.2012-0635-OA.

 

Bishop JA, Teruya-Feldstein J, Westra WH, Pelosi G, Travis WD, et al. (2012) p40 (ΔNp63) is superior to p63 for the diagnosis of pulmonary squamous cell carcinoma. Mod Pathol 25: 405–415. doi:10.1038/modpathol.2011.173.

 

Rossi G, Pelosi G, Barbareschi M, Graziano P, Cavazza A, et al. (2013) Subtyping Non-Small Cell Lung Cancer: Relevant Issues and Operative Recommendations for the Best Pathology Practice. International Journal of Surgical Pathology 21: 326–336. doi:10.1177/1066896913489346.

 

Gailey MP, Bellizzi AM (2013) Immunohistochemistry for the novel markers glypican 3, PAX8, and p40 (ΔNp63) in squamous cell and urothelial carcinoma. Am J Clin Pathol 140: 872–880. doi:10.1309/AJCP4NSKW5TLGTDS.

PAX-8 along with PAX-2 are transcription factors (nuclear expression) important in the development of Mullein system, kidney, and thyroid.  They both are expressed in normal kidney and most renal neoplasms.  PAX-8 expression may also be seen in carcinomas of the lower urinary tract and nephrogenic adenomas.  In the study by Ozacan et. al., PAX-8 had better performance characteristics than PAX-2.

 

PAX-8 is not expressed in cancers from rectum, pituitary, adrenal, colon, prostate, breast, lung, stomach, liver, soft tissue, melanoma, and lymphoma.  The rabbit monoclonal PAX-8 antibody shows staining in lymph nodes, pancreas, and stomach/colon neuroendocrine cells.  The mouse PAX-8 antibody clone BC12 does not appear to have expression in lymph nodes, pancreas and stomach/colon neuroendocrine cells. (Tacha, D., et. al.)  In an experience by Ortiz-Rey, et al., they found PAX-8 to be helpful in differentiated seminal vesicle epithelium from prostate epithelium in needle core biopsies.  Sometimes this can be difficult to differentiate from carcinoma, and could be helpful in a panel to differentiate epithelial types.

 

Ozcan, A., et. al.

 

Galley, M.P., et. al.

 

Normal Tissue Expression for PAX-8  (Chan, J.K.C.)

 

References:

Shen, SS. “Role of Immunohistochemistry in Diagnosing Renal Neoplams: When Is It Really Useful?”Arch Pathol Lab Med, Vol. 136, April 2012.  pp. 410-417. 

 

Al-Ghawi, H., Asojo, O. A., Truong, L. D., Ro, J. Y., Ayala, A. G., & Zhai, Q. J. (2010). Application of Immunohistochemistry to the Diagnosis of Kidney Tumors. Pathology Case Reviews, 15(1), 25–34. doi:10.1097/PCR.0b013e3181d51c70 

 

Ozcan, A., la Roza, de, G., Ro, J. Y., Shen, S. S., & Truong, L. D. (2012). PAX2 and PAX8 expression in primary and metastatic renal tumors: a comprehensive comparison. Archives of Pathology & Laboratory Medicine, 136(12), 1541–1551. doi:10.5858/arpa.2012-0072-OA 

 

Chan, J. K. C. (2013). Newly Available Antibodies With Practical Applications in Surgical Pathology. International Journal of Surgical Pathology, 21(6), 553–572. doi:10.1177/1066896913507601 

 

Gailey, M. P., & Bellizzi, A. M. (2013). Immunohistochemistry for the novel markers glypican 3, PAX8, and p40 (ΔNp63) in squamous cell and urothelial carcinoma. American Journal of Clinical Pathology, 140(6), 872–880. doi:10.1309/AJCP4NSKW5TLGTDS 

 

Tacha, D., Qi, W., Zhou, D., Bremer, R., & Cheng, L. (2013). PAX8 mouse monoclonal antibody [BC12] recognizes a restricted epitope and is highly sensitive in renal cell and ovarian cancers but does not cross-react with b cells and tumors of pancreatic origin. Applied Immunohistochemistry & Molecular Morphology : AIMM / Official Publication of the Society for Applied Immunohistochemistry, 21(1), 59–63. doi:10.1097/PAI.0b013e318257cc1c 

 

Ortiz-Rey – PAX8 AIMM editorial

PAX-5 (B-cell specific activator protein: BSAP) is a nuclear transcription marker that is normally found onPre-B and mature B-lymphocytes (not plasma cells).  Expression is seen in Pre-B ALL, B-cell lymphomas and classical Hodgkin lymphoma (>90%, dimmer expression compared to background B-cells), but not plasmacytomas.  It should be noted that some cases of small cell carcinoma (73%), Merkel cell carcinoma (93%), and alveolar rhabdomyosarcoma may show PAX-5 expression.

 

PAX-5 is particularly useful in evaluating cases of B-cell lymphomas, which have been treated with rituximab.  At some point during treatment, approximately 20% of these cases treated with rituximab therapy may lose expression of CD20 (flow cytometry appears to be more sensitive in detecting down regulation of CD20 with rituximab therapy).  PAX-5 is helpful in identifying such B-cell with loss of CD20 expression.  This is important clinically, because such cases may not respond to additional rituximab therapy.  It is important to note that there may be down regulation of other B-cell markers with rituximab therapy.  In a relatively small set of cases by Chu, PG, et al, PAX-5 expression was present in 21 of 24 cases of CD20 negative mature B-cell neoplasms treated with rituximab.  Therefore, a panel of B-cell markers may be needed in cases treated with rituximab.

Hadi Yaziji, AIMM Annual Meeting, “New Antibodies in Diagnostic Immunohistochemistry”, presentation, 2010.

 

AJSP 2005;29:687

 

Bone Marrow IHC.  Torlakovic, EE, et. al. American Society for Clinical Pathology Pathology Press © 2009.  pp. 221.

 

Chu, P. G., Loera, S., Huang, Q., & Weiss, L. M. (2006). Lineage Determination of CD20- B-Cell Neoplasms: An Immunohistochemical Study. American Journal of Clinical Pathology, 126(4), 534–544. doi:10.1309/3WG32YRAMQ7RB9D4 

PAX-2 is nuclear marker that is expressed in early renal organogenesis.  It appears to be a sensitive marker of renal cell carcinoma.   However, caution should be applied in the setting of papillary neoplasms (particularly uterine and ovarian serous papillary carcinomas).

 

PAX-8 along with PAX-2 are transcription factors (nuclear expression) important in the development of mullein, kidney, and other organs.  They both are expressed in normal kidney and most renal neoplasms.  However, PAX-2 is typically negative in thyroid neoplasms.

 

Ozcan, A., et. al. (PAX-2 and PA-8 expression in various renal tumors)

 

Sharma, S.G., et. al.  (PAX-2 and RCCma expression in various papillary tumors)

 

References:

Hadi, AIMM Annual Meeting, “Carcinomas of Unknown Primary”, presentation, 2011.

 

Mazal PR et al.  Mod Pathol 2005;18:535-540.

 

Shen, SS. “Role of Immunohistochemistry in Diagnosing Renal Neoplams: When Is It Really Useful?”Arch Pathol Lab Med, Vol. 136, April 2012.  pp. 410-417. 

 

Ozcan, A., la Roza, de, G., Ro, J. Y., Shen, S. S., & Truong, L. D. (2012). PAX2 and PAX8 expression in primary and metastatic renal tumors: a comprehensive comparison. Archives of Pathology & Laboratory Medicine, 136(12), 1541–1551. doi:10.5858/arpa.2012-0072-OA  

 

Sharma, S. G., Gokden, M., McKenney, J. K., Phan, D. C., Cox, R. M., Kelly, T., & Gokden, N. (2010). The utility of PAX-2 and renal cell carcinoma marker immunohistochemistry in distinguishing papillary renal cell carcinoma from nonrenal cell neoplasms with papillary features. Applied Immunohistochemistry & Molecular Morphology : AIMM / Official Publication of the Society for Applied Immunohistochemistry, 18(6), 494–498. doi:10.1097/PAI.0b013e3181e78ff8 

NKX3.1 is a prostate specific homeobox gene (chromosome 8p21), which as an immunohistochemisry IHC marker has shown specificity for prostate epithelium and prostate adenocarcinomas.  Normal IHC expression is found in the nucleus of benign and malignant prostate glands.  Unfortunately, like most other markers, it is not completely specific.  Occasional mucous glands in the lung, testis, and scattered ureteral epithelial cells have shown expression (Brown, et. al.)

 

Two important points: (1) expression (sensitivity) decreases with hormone refractoriness and advanced stage (metastasis), and (2) expression appears independent of Gleason score (Brown, et al.).  In a related article by Mohanty et. al., they showed NKX3.1 to be very sensitive (100%) and specific (100%) in the setting of poorly differentiated prostate adenocarcinomas located in the bladder trigone with the differential diagnosis of urothelial carcinoma.

 

NKX3.1 may be a potential prognostic marker of progression and hormone refractoriness in low stage patients, but this needs further study (Brown, et. al.).  However, due to limited sensitivity in metastatic disease, this marker appears to have limited use in the workup of carcinomas of unknown primary site (CUPS).

 

Table 1.  Expression characteristics of NKX3.1

 

Mohanty SK, Smith SC, Chang E, et al. Evaluation of contemporary prostate and urothelial lineage biomarkers in a consecutive cohort of poorly differentiated bladder neck carcinomas. Am J Clin Pathol. 2014;142(2):173–183. doi:10.1309/AJCPK1OV6IMNPFGL.

 

 Bowen C, Bubendorf L, Voeller HJ, et al. Loss of NKX3.1 expression in human prostate cancers correlates with tumor progression. Cancer Res. 2000;60(21):6111–6115.