Figure 3 (IMAGE) Impact Journals LLC Caption Hierarchical clustering of tonsil squamous cell carcinoma cohorts based on viral signature detection pattern with associated pathological features (perineural invasion (PNI), lymphovascular invasion (LVI), and tumor stage (T stage)). Hierarchical clustering for HPV16 (A) and HPV18 (B) viral probes are represented as heat maps for each cohort. Clustering was performed by R program using Euclidean distance, complete linkage and non-adjusted values. Clustering of the samples using NBClust software [Calinski and Harabasz index, Euclidean distance, complete linkage]. Chi-square test was applied and showed no significant differences of proportions of tumor stage (T1 versus T2), PNI, and LVI in different hierarchical clusters of cancer samples. NPR ("negative-node primary"), PPR ("positive-node primary"), NLN ("negative lymph node"), PLN ("positive lymph node"), CTRL ("control"), HPV (human papilloma virus), PNI (perineural invasion), LVI (lymphovascular invasion), T stage (tumor stage). Credit Correspondence to - Erle S. Robertson - erle@pennmedicine.upenn.edu Usage Restrictions CCBY License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.