TTF-1 Expression in Breast Carcinoma—The Chosen Clone Matters

The Incidence of Labelling of Non-Lung Adenocarcinomas With Antibodies Against TTF-1 and Diagnostic Implications

Thyroid transcription factor 1 (TTF-1) is an immunohistochemical marker in the identification of lung and thyroid tumors. However, positive labelling for TTF-1 can occur in tumors from other sites, and this can result in misdiagnosis if only a limited panel of antibodies is used. We assessed the frequency of expression of 3 TTF-1 antibody clones, namely, 8G7G3/1, SPT24, and SP141 on a tissue microarray of 104 colorectal cancer (CRC), and whole-tumor sections of 165 CRC with known microsatellite instability (MSI) status. We also analyzed the expression of TTF-1 in a tissue microarray of 112 prostatic adenocarcinomas. The association of TTF-1 expression with clinicopathologic parameters and patient survival was analyzed. Six of 104 (5.7%) primary colorectal carcinomas expressed TTF-1 with SPT24 and SP141 clones, whereas only 2 (2%) of these tumors labeled positive for TTF-1 with clone 8G7G3/1. A significant association of TTF-1 expression with younger age at diagnosis (P=0.001) was found, but not with stage, or survival. The SP141 clone also labelled 24/165 (14.5%) of 165 CRC with known MSI status. There was an association with younger age (P<0.001), but not with MSI status or survival. TTF-1 expression was found in 39/112 (34%) prostate adenocarcinomas with 6/112 (5.3%) labelling with clone 8G7G3/1, 26/112 (23%) with clone SP141, and 31/112 (28%) with clone SPT24. TTF-1 expression appeared to be associated with extracapsular extension (P=0.022) and with higher stage (P=0.039). Here too TTF-1 expression was not associated with survival. The mRNA expression of TTF-1 in these tumors was confirmed by RTPCR, indicating that this is not false-positive labelling. Depending on the clone used, TTF-1 expression can vary with the SP141 and SPT24 clones exhibiting higher incidence of labelling. Pathologists should be aware of the differences in performance profiles of the different TTF-1 clones in diagnostic practice.

Diagnostic and Predictive Immunohistochemistry for Non-Small Cell Lung Carcinomas

Non-small cell lung carcinoma (NSCLC) accounts for significant morbidity and mortality worldwide, with most patients diagnosed at advanced stages and managed increasingly with targeted therapies and immunotherapy. In this review, we discuss diagnostic and predictive immunohistochemical markers in NSCLC, one of the most common tumors encountered in surgical pathology. We highlight 2 emerging diagnostic markers: nuclear protein in testis (NUT) for NUT carcinoma; SMARCA4 for SMARCA4-deficient thoracic tumors. Given their highly aggressive behavior, proper recognition facilitates optimal management. For patients with advanced NSCLCs, we discuss the utility and limitations of immunohistochemistry (IHC) for the "must-test" predictive biomarkers: anaplastic lymphoma kinase, ROS1, programmed cell death protein 1, and epidermal growth factor receptor. IHC using mutant-specific BRAF V600E, RET, pan-TRK, and LKB1 antibodies can be orthogonal tools for screening or confirmation of molecular events. ERBB2 and MET alterations include both activating mutations and gene amplifications, detection of which relies on molecular methods with a minimal role for IHC in NSCLC. IHC sits at the intersection of an integrated surgical pathology and molecular diagnostic practice, serves as a powerful functional surrogate for molecular testing, and is an indispensable tool of precision medicine in the care of lung cancer patients.

An immunohistochemical comparison of two TTF-1 monoclonal antibodies in atypical squamous lesions and sarcomatoid carcinoma of the lung, and pleural malignant mesothelioma

Immunohistochemical detection of thyroid transcription factor-1 (TTF-1) plays an important role in the diagnosis and subclassification of non-small cell carcinomas of the lung in biopsy and some cytology samples, specifically for identification of squamous cell carcinoma (classically negative) and non-mucinous adenocarcinoma (positive in most cases) and for discrimination between lung adenocarcinoma and pleural malignant mesothelioma (classically negative).

Metastatic carcinoma of unknown primary: diagnostic approach using immunohistochemistry

Carcinoma of unknown primary origin (CUP) is one of the 10 most prevalent malignancies. CUP patients in whom a site of origin can be ascribed have better outcomes than those in which the primary tumor remains unidentified. Among the tools available to pathologists in approaching these lesions, immunohistochemistry is a reliable, inexpensive, and widely available resource. New markers continue to emerge, which, in combination with other historically useful antibodies, allow rapid and accurate identification of primary site in an increasing number of cases. This review discusses the approach to the diagnosis of CUP using immunohistochemistry and outlines some of the most useful markers with a particular focus on the utility of lineage-restricted transcription factors, including CDX2, NKX3-1, PAX8, SATB2, TTF-1, and SF1.

Expression of thyroid transcription factor-1 is associated with a basal-like phenotype in breast carcinomas

Background

The differential diagnosis between primary and secondary breast cancers might be difficult, especially in poorly differentiated tumors. Thyroid Transcription Factor-1 (TTF-1) has been regarded as a reliable marker for lung or thyroid origin, with only occasional positive staining in other tumors. However, positive cases have recently been reported among primary breast carcinomas.

Methods and results

Here, we analyzed expression of TTF-1 protein (clone SPT24) by immunohistochemical staining of sections from paraffin embedded tumor samples in 247 primary breast cancers from the population-based Norwegian Breast Cancer Screening Program. Positive staining (weak or strong) was observed in 7 cases (2,8%). As novel observations, positivity was demonstrated more frequently in estrogen receptor negative cases (14,0% vs. 1,4%; p = 0,004), highly proliferative tumors (8,8% vs. 1,1%; p = 0,008), tumors with a basal-like phenotype by showing expression of CK5/6 and/or P-cadherin (11,1% vs. 1,4%; p = 0,01), and tumors with blood vessel invasion (9,7% vs. 1,9%; p = 0,04). Also, TTF-1 was associated with histological grade 3 tumors compared with grade 1 or 2 tumors (7,7% vs. 1,5%; p = 0,04) as well as lymph node positive cases (5,2% vs. 1,8%; p = 0,03).

Conclusions

Our population-based findings indicate that TTF-1 may be positive in approximately 3% of primary breast cancers, and positivity indicates an association with adverse prognostic factors.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8313753509421182

Comparison of monoclonal napsin A, polyclonal napsin A, and TTF-1 for determining lung origin in metastatic adenocarcinomas

Thyroid transcription factor 1 (TTF-1) is currently the best immunohistochemical marker for carcinomas of lung origin. Our aim was to compare napsin A to TTF-1 for identifying pulmonary origin in metastatic adenocarcinoma and its mimics. One hundred fifty-five metastatic carcinomas (55 pulmonary, 100 nonpulmonary) were stained with monoclonal napsin A and TTF-1, and most also with polyclonal napsin A. The sensitivity of monoclonal napsin A, polyclonal napsin A, and TTF-1 for metastatic adenocarcinomas of pulmonary origin was 76%, 81%, and 82%, respectively. Two lung carcinomas were diffusely positive for monoclonal napsin A, but negative or equivocal for TTF-1. TTF-1 stained 9 of 100 nonpulmonary carcinomas (all thyroid), monoclonal napsin A stained 12 of 100 (4 sites), and polyclonal napsin A stained 27 of 91 (8 sites). Napsin A is expressed in a wider variety of metastatic nonpulmonary carcinomas than TTF-1, and the monoclonal antibody is more specific. Napsin A is a useful adjunct to TTF-1, because occasional lung adenocarcinomas are TTF-1 negative but napsin A positive.

Metastases to and from the Breast

Breast cancer is a common source of systemic metastatic disease. Distinguishing metastatic breast cancer from other types of malignancies can be diagnostically challenging but is important for correct treatment and prognosis. Nonmammary tumors can also metastasize to the breast, although this is a rare phenomenon. Differentiating a metastasis to the breast from a primary breast cancer can likewise be difficult. Knowledge of the clinical history and careful morphologic evaluation are the cornerstones of diagnosis. A panel of immunohistochemical stains tailored to the differential diagnosis at hand can provide helpful information in ambiguous cases.

Thyroid paraganglioma. Report of 3 cases and description of an immunohistochemical profile useful in the differential diagnosis with medullary thyroid carcinoma, based on complementary DNA array results

Thyroid paraganglioma is a rare disorder that sometimes poses problems in differential diagnosis with medullary thyroid carcinoma. So far, differential diagnosis is solved with the help of some markers that are frequently expressed in medullary thyroid carcinoma (thyroid transcription factor 1, calcitonin, and carcinoembryonic antigen). However, some of these markers are not absolutely specific of medullary thyroid carcinoma and may be expressed in other tumors. Here we report 3 new cases of thyroid paraganglioma and describe our strategy to design a diagnostic immunohistochemical battery. First, we performed a comparative analysis of the expression profile of head and neck paragangliomas and medullary thyroid carcinoma, obtained after complementary DNA array analysis of 2 series of fresh-frozen samples of paragangliomas and medullary thyroid carcinoma, respectively. Seven biomarkers showing differential expression were selected (nicotinamide adenine dinucleotide dehydrogenase 1 alpha subcomplex, 4-like 2, NDUFA4L2; cytochrome c oxidase subunit IV isoform 2; vesicular monoamine transporter 2; calcitonin gene-related protein/calcitonin; carcinoembryonic antigen; and thyroid transcription factor 1) for immunohistochemical analysis. Two tissue microarrays were constructed from 2 different series of paraffin-embedded samples of paragangliomas and medullary thyroid carcinoma. We provide a classifying rule for differential diagnosis that combines negativity or low staining for calcitonin gene-related protein (histologic score, <10) or calcitonin (histologic score, <50) together with positivity of any of NADH dehydrogenase 1 alpha subcomplex, 4-like 2; cytochrome c oxidase subunit IV isoform 2; or vesicular monoamine transporter 2 to predict paragangliomas, showing a prediction error of 0%. Finally, the immunohistochemical battery was checked in paraffin-embedded blocks from 4 examples of thyroid paraganglioma (1 previously reported case and 3 new cases), showing also a prediction error of 0%. Our results suggest that the comparative expression profile, obtained by complementary DNA arrays, seems to be a good tool to design immunohistochemical batteries used in differential diagnosis.