Stains & molecular markers
Napsin A
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Napsin A
Napsin A
Author: Nat Pernick, M.D.
Topic Completed: 1 June 2012
Minor changes: 29 October 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Napsin A
Table of Contents
Definition / general | Uses by pathologists | Microscopic (histologic) images | Cytology images | Positive staining - normal | Positive staining - disease | Electron microscopy imagesCite this page: Pernick N. Napsin A. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsnapsina.html. Accessed January 22nd, 2021.
Definition / general
- A novel aspartic proteinase of the pepsin family involved in the maturation of surfactant protein B
- Found primarily in lung and kidney
- Lack of Napsin A expression in tumor cells may be poor prognostic marker in pulmonary adenocarcinoma (Lung Cancer 2012;77:156)
Uses by pathologists
- Useful individually (Am J Surg Pathol 2012;36:396) or as part of panel (Arch Pathol Lab Med 2012;136:155, Appl Immunohistochem Mol Morphol 2012;20:350) to distinguish lung adenocarcinoma (positive) from squamous cell carcinoma (negative in tumor cells but positive in hyperplastic type II pneumocytes and intra-alveolar macrophages entrapped within tumor cells)
- Useful as part of panel to classify poorly differentiated non small cell lung carcinoma on small biopsies (Am J Surg Pathol 2011;35:15), fine needle aspirates (Cytojournal 2012;9:10) or bronchial brushings (Cancer Cytopathol 2011;119:335)
- Superior to TTF1 in distinguishing primary lung adenocarcinoma from other carcinomas (except kidney), particularly primary lung small cell carcinoma and primary thyroid carcinoma (Arch Pathol Lab Med 2012;136:163)
- Superior to TTF1 in distinguishing metastatic pulmonary (positive) from nonpulmonary (negative) adenocarcinoma in cell blocks prepared from malignant pleural effusions (Acta Cytol 2011;55:266) or from fine needle aspirates (Cancer Cytopathol 2011;119:127)
- May help identify metastatic disease with unknown primary as originating in lung (Case Rep Oncol 2011;4:564)
- May help distinguish lung primaries from metastases to lung, as part of panel (Biotech Histochem 2012;87:30)
Microscopic (histologic) images
Contributed by Andrey Bychkov, M.D., Ph.D.
Lung ADC
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Lung adenocarcinoma
Cerebellar tumor specimen
Cytology images
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Pulmonary ADC
Pulmonary SCC
SCC
ADC
PDC
Positive staining - normal
- Type 2 pneumocytes (cytoplasm), alveolar macrophages (cytoplasm) (Hum Pathol 2010;41:20)
Positive staining - disease
- Renal cell carcinoma: papillary (80%), clear cell (33%, Appl Immunohistochem Mol Morphol 2011;19:313)
- Pulmonary adenocarcinoma
- Ovarian clear cell carcinoma (Mod Pathol 2015;28;111)
- Thyroid carcinoma: anaplastic (15%, Am J Surg Pathol 2013;37:1215), micropapillary (2 of 2), papillary (5% [2 cases, both were tall cell], Hum Pathol 2010;41:20), poorly differentiated (13%)
Electron microscopy images
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Type II pneumocytes
