Cervical Cancer, TERC, FISH

This is a fluorescence in situ hybridization (FISH)-based assay performed using ThinPrep^® or SurePath™ cervical cytology samples. This test determines the number of copies of TERC, a telomerase RNA component gene located at chromosome band 3q26. Two fluorescent probes are used to calculate a ratio between copy number for chromosome 3, measured by a peri-centromeric probe (green signals below), and the copies of the TERC gene locus (red signals below). The pattern of these two probes in each cell can thus be scored as non-amplified, TERC-amplified, or polysomic. Interpretation is based on the pattern and number of cells with either abnormal pattern.

There are several important events that occur as cervical cells transition from normal to malignant. The earliest event is initiated by infection of cervical squamous cells by high-risk subtypes of human papilloma virus (HPV). This is followed by chromosomal instability, which manifests as polysomy (ie, increase in chromosome copy number), and by TERC gene amplification.

The earlier HPV-related cellular changes are associated on a Pap smear with koilocytosis and low-grade dysplasia. The later genomic changes, such as genetic instability and TERC amplification, are associated with high-grade squamous intraepithelial neoplasia (HSIL) and progression to invasive carcinoma.

Consider using this test as an adjunct to Pap smear cytomorphology and high-risk HPV testing, especially when

• Your patient has atypical Pap test results, particularly in assessing the significance of ASC-H lesions
• You want to stratify LSIL lesions into those with a higher risk of progression to HSIL
• Your patient has atypical Pap test results with a negative high-risk HPV test result

This assay can help you decide how best to manage the patient by providing additional information not available from cytology or HPV testing. Since TERC amplification is associated with HSIL, you may wish to consider more intensive follow-up for patients who have an atypical cytology result such as ASC-H that is associated with TERC amplification. Similarly, this assay may provide additional information in patients with atypical Pap findings but absence of high-risk HPV.

Information provided by this test is additive to cytology findings and largely independent of HPV infection status. Although not included in the ACOG or ASCP guidelines, TERC copy number enumeration has been shown in several large studies summarized below to be useful in predicting progression in SILs. Test results will have the greatest impact on influencing appropriate follow-up interval or treatment plan when Pap test results are equivocal or when cytology and HPV test results are discordant.

Yes, there have been a number of peer-reviewed journal articles published that establish the power of detecting TERC amplification and using it to further stratify patients with cervical dysplasia. Key references include:

• Heselmeyer-Haddad K, et al. Genomic amplification of the human telomerase gene (TERC) in Pap smears predicts the development of cervical cancer. Am J Pathol. 2005;166:1229-1238.
• This study of 59 patients with LSIL/CIN1/CIN2 lesions showed that gain of 3q/TERC was associated with progression to CIN3/HSIL rather than regression on follow-up analysis.
• Zheng Tu, et al. Genomic amplification of the human telomerase RNA gene for differential diagnosis of cervical disorders. Cancer Genet Cytogenet. 2009;191:10-16.

This large study, that included over 1000 women, demonstrated a strong positive correlation between TERC amplification and advancing lesion grade as determined by both cytopathology and histopathology.

• Andersson S, et al. Detection of genomic amplification of the human telomerase gene (TERC), a potential marker for triage of women with HPV-positive, abnormal Pap smears. Am J Pathol. 2009;175:1831-1847.

This study of 78 cytology samples demonstrated positive correlation between TERC amplification and histologically confirmed advancing lesion grade.

Several recent studies have confirmed these findings:

• Zappacosta R, et al. Clinical role of the detection of human telomerase RNA component gene amplification by fluorescence in situ hybridization on liquid-based cervical samples: Comparison with human papillomavirus-  DNA testing and histopathology. Acta Cytol. 2015;59:345-354.
• Li L, et al. Prospective study of hTERC gene detection by fluorescence in situ hybridization (FISH) in cervical     intraepithelial neoplasia 1 natural prognosis. Eur J Gynaecol Oncol. 2014;35:289-291.
• Zhao XY, et al. Human telomerase gene and high-risk human papillomavirus infection are related to cervical   intraepithelial neoplasia. Asian Pac J Cancer Prev. 2015;16:693-697.

The test can be performed using residual liquid-based cytology samples (ThinPrep® or SurePath™) collected for Pap testing. These samples can be tested up to 30 days after collection, providing an adequate number of cervical epithelial cells can be harvested.

The test cannot be performed on slides from conventional Pap smear samples.

The analytical sensitivity and specificity of this assay approach 100%.

In our validation study, TERC amplification or polysomy of chromosome 3 was not observed in cytology samples with normal/benign results, but in ~10% of LSIL, up to 30% of ASC-H and over 90% of HSIL cases. These results are similar to those noted in previous studies correlating alterations of the TERC locus with Pap cytology findings (eg, Cancer Genet Cytogenet. 2009;191:10-16).