Test Catalog

Test ID: TTF40    
TTF41 (SPT24) + p40 Immunostain, Technical Component Only

Useful For Suggests clinical disorders or settings where the test may be helpful

Thyroid transcription factor 1 aids in the classification of carcinomas of unknown origin


p40 aids in the classification of carcinomas and lymphomas

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Thyroid transcription factor 1 (TTF1) is a nuclear protein (detected by the chromogen 3,3'-diaminobenzidine: DAB) expressed in thyroid follicular cells, type II pneumocytes, and a subset of bronchial cells. The p40 antibody recognizes the deltaNp63 isoform of p63 (detected by the chromogen fast red). The predominant localization of p40 is in the basal layer of the stratified squamous and transitional epithelia. Given the relative specificity of TTF1 for cells of thyroid or lung origin, TTF1 is often included in a panel to identify the primary site for carcinomas of unknown origin. The p40 antibody may help to distinguish squamous cell carcinomas from other non-small cell carcinomas.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Interpretation Provides information to assist in interpretation of the test results

This test includes only technical performance of the stain (no pathologist interpretation is performed). If diagnostic consultation by a pathologist is required order PATHC / Pathology Consultation.


The positive and negative controls are verified as showing appropriate immunoreactivity. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request. Contact 855-516-8404.


Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen-dependent. Best practice is for paraffin sections to be cut within 6 weeks.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Pelosi G, Fabbri A, Tamborini E, et al: Challenging Lung Carcinoma with Coexistent ?Np63/p40 and Thyroid Transcription Factor-1 Labeling Within the Same Individual Tumor Cells. J Thorac Oncol 2015 Oct;10(10):1500-1502

2. Whithaus K, Fukuoka J, Prihoda TJ, et al: Evaluation of napsin A, cytokeratin 5/6, p63, and thyroid transcription factor 1 in adenocarcinoma versus squamous cell carcinoma of the lung. Arch Pathol Lab Med 2012 Feb;136(2):155-162

3. Sterlacci W, Savic S, Schmid T, et al: Tissue-Sparing Application of the Newly Proposed IASLC/ATS/ERS Classification of Adenocarcinoma of the Lung Shows Practical Diagnostic and Prognostic Impact. AJCP 2012;137:946-956