Describe the management of a metastatic neck node with an unknown primary.

Metastatic Neck Node with an Unknown Primary

• A carcinoma of unknown primary (cup) in the neck is a cervical node containing metastatic carcinoma in which NO primary tumour is found after a thorough and systematic search.
• It represents a small proportion of head and neck cancers, and its management is a disciplined sequence rather than a guess.
• The histology directs the search, so it is established first:
• Squamous carcinoma — the primary is almost always in the upper aerodigestive tract, and most often in the tonsil or the tongue base, both of which have deep crypts in which a small primary hides
• Adenocarcinoma — suggests a salivary, thyroid or infraclavicular primary (lung, breast, stomach, gastrointestinal tract, ovary, prostate)
• Undifferentiated carcinoma with EBV — points strongly to the nasopharynx
• Papillary carcinoma with thyroglobulin — the thyroid
• Melanoma — the scalp, skin, mucosa or eye, so those must be examined specifically
• The level OF the node also predicts the site — levels II and III suggest the oropharynx, oral cavity, larynx or hypopharynx; level V suggests the nasopharynx; and supraclavicular (level IV or V low) suggests an infraclavicular primary.
• The sequence OF investigation, and its order is the answer:
• 1. A meticulous clinical examination — the entire upper aerodigestive tract with flexible nasendoscopy, palpation of the tongue base, tonsil and floor of mouth, and examination of the scalp, skin, ears, thyroid and breasts
• 2. Ultrasound-guided FNAC of the node, with p16 and HPV testing, EBV testing, and thyroglobulin washout as indicated by the cytology
• 3. Imaging before endoscopy — pet-CT is performed before panendoscopy and biopsy.
• Pet-CT identifies a primary in a useful proportion of otherwise occult cases, and also detects distant disease
• 4. Examination under anaesthesia with panendoscopy and directed biopsies of any suspicious area, plus blind biopsies of the nasopharynx, tongue base and pyriform fossae
• 5. Ipsilateral tonsillectomy, which is diagnostic and identifies a primary in a significant proportion; and tongue base mucosectomy, increasingly performed with transoral robotic surgery, which has substantially improved the primary detection rate
• Bilateral tonsillectomy is performed by some.
• Never perform an open biopsy of the node before this sequence is complete, for the reasons given elsewhere — seeding, higher recurrence and a compromised neck dissection
• Treatment once the search is exhausted — neck dissection with radiotherapy, or primary chemoradiotherapy, decided by nodal stage and fitness