PTK7 and head and neck squamous cell carcinoma: As shown in Table 1 and Fig. 1h, high PTK7 expression levels were associated with a poor histological grade, a larger tumor size (greater than 4 cm in diameter), and nodal metastasis in the HNSCC specimens; however, PTK7 expression levels were not associated with the following parameters: age, gender, smoking, alcohol, and local recurrence.