Stains & CD markers

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Last staff update: 13 June 2022

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PubMed Search: deltaNp63 (p40)

Jaya Ruth Asirvatham, M.D.
Page views in 2023: 27,492
Page views in 2024 to date: 13,151
Cite this page: Asirvatham JR. p40. website. Accessed June 16th, 2024.
Definition / general
Essential features
  • Nuclear marker with expression in squamous, urothelial, myoepithelial / basal cell differentiation
  • More specific for squamous cell differentiation than p63 in lung carcinoma (Mod Pathol 2012;25:405)
  • Recommended for subtyping non small cell carcinoma (J Thorac Oncol 2019;14:377)
Clinical features
  • Mutations cause ectrodactyly ectodermal dysplasia cleft syndrome, ankyloblepharon ectodermal dysplasia clefting syndrome, nonsyndromic split hand / split foot malformation (J Cell Sci 2011;124:2200)
  • Nuclear stain
Uses by pathologists
  • Usually positive in squamous, urothelial and myoepithelial / basal cell differentiation
  • Part of recommended panel for subtyping non small cell lung carcinoma (J Thorac Oncol 2019;14:377)
Microscopic (histologic) images

Contributed by Jaya Ruth Asirvatham, M.B.B.S. and Andrey Bychkov, M.D., Ph.D.

Squamous mucosa

Squamous cell carcinoma, tonsil

Basaloid neoplasm

Lung squamous cell carcinoma

Lung squamous cell carcinoma

Positive staining - normal
Positive staining - disease
Negative staining
Sample pathology report
  • Cervix, biopsy:
    • Invasive squamous cell carcinoma, poorly differentiated
    • Ancillary studies: The malignant cells are diffusely positive for cytokeratin 5/6, p40 and p16 and are negative for cytokeratin 7, supporting the diagnosis.
Board review style question #1

A 55 year old male construction worker with a 20 pack year smoking history and no prior diagnosis of malignancy, presents with a lung mass, which is biopsied. The biopsy demonstrates a poorly differentiated malignant neoplasm. An immunohistochemical panel comprising CK7, CK20, CK5/6, TTF1, p40, napsin, calrentin and BerEP4 is performed.

Which profile supports the diagnosis of squamous cell carcinoma?

  1. CK7+, TTF1+, napsin+, other stains negative
  2. CK5/6+, p40+ in more than 50% of cells, strong, other stains negative
  3. CK7+, CK5/6+, TTF1+, p40+ in less than 50% of cells strong, other stains negative
  4. CK5/6+, calretinin+, others negative
  5. CK20+, others negative
Board review style answer #1
B. CK5/6+, p40+ in more than 50% of cells, strong, other stains negative. Strong p40 staining in greater than 50% of cells is expected in squamous cell carcinoma. Profile A is seen in lung adenocarcinoma. Profile C is supportive of lung adenosquamous carcinoma. Profile D is consistent with mesothelioma. Metastatic colorectal carcinoma is a possibility with profile E. A diagnosis of primary squamous cell carcinoma of the lung needs to be made in the appropriate clinical context, as metastatic squamous cell carcinoma or direct extension from a thymic carcinoma may have the same profile. PAX8 and CD117 are often positive in thymic carcinomas and will be negative in primary lung squamous cell carcinoma.

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Reference: p40
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