Evaluation Criteria for Chromosome Instability Detection by FISH to Predict Malignant Progression in Premalignant Glottic Laryngeal Lesions

SIMPLE SUMMARY: Head and neck cancer develops from premalignant lesions. The key issue is to recognize potentially harmful precursor lesions. Fluorescence in Situ Hybridization (FISH)-based detection of copy number variations (CNV) of chromosomes 1 and 7 can help to differentiate between low-risk and high-risk lesions. Dual-target FISH for chromosomes 1 and 7 in 87 glottic, laryngeal premalignancies was performed. Lesions were evaluated by (1) establishing the chromosome 7/1 ratio (CR-FISH), based on the absolute number of signals of both chromosomes in 100 nuclei, and (2) by the assessment of the percentage of aberrant nuclei, counted in a total of 100 (PAN-FISH). The latter approach combined with histopathological assessment was the best predictive model for progression. The defined evaluation criteria for FISH diagnostics and the proposed prognostic model may help in clinical decision making on treatment strategies in patients with laryngeal precursor lesions. ABSTRACT: Background: The definition of objective, clinically applicable evaluation criteria for FISH 1c/7c in laryngeal precursor lesions for the detection of chromosome instability (CI). Copy Number Variations (CNV) for chromosomes 1 and 7 reflect the general ploidy status of premalignant head and neck lesions and can therefore be used as a marker for CI. Methods: We performed dual-target FISH for chromosomes 1 and 7 centromeres on 4 µm formalin-fixed, paraffin-embedded tissue sections of 87 laryngeal premalignancies to detect CNVs. Thirty-five normal head and neck squamous cell samples were used as a control. First, the chromosome 7:1 ratio (CR) was evaluated per lesion. The normal range of CRs (≥0.84 ≤ 1.16) was based on the mean CR +/− 3 x SD found in the normal population. Second, the percentage of aberrant nuclei, harboring > 2 chromosomes of chromosome 1 and/or 7 (PAN), was established (cut-off value for abnormal PAN ≥ 10%). Results: PAN showed a stronger correlation with malignant progression than CR (resp. OR 5.6, p = 0.001 and OR 3.8, p = 0.009). PAN combined with histopathology resulted in a prognostic model with an area under the ROC curve (AUC) of 0.75 (s.e. 0.061, sensitivity 71%, specificity 70%). Conclusions: evaluation criteria for FISH 1c/7c based on PAN ≥ 10% provide the best prognostic information on the risk of malignant progression of premalignant laryngeal lesions as compared with criteria based on the CR. FISH 1c/7c detection can be applied in combination with histopathological assessment.