A patient presented with a 3.5-cm size lymph node enlargement, which was hard and present in the submandibular region. Examination of the head and neck did not yield any lesion. Which of the following investigations should follow?

Suspected lymph node may have metastases from the upper aerodigestive tract. Since no lesion is found on physical examination of head and neck, triple endoscopy would be justified next. Supravital staining helps in selecting the site of biopsy in a lesion. As no lesion is discovered, it will not be very useful.