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Lymph Node Metastasis from Unknown Primary (CUP) - Head & Neck

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1. What is CUP?

• Thorough clinical examination
• Cross-sectional imaging (CT/MRI)
• Examination under anaesthesia (EUA) with tonsillectomy and tongue base biopsy

True CUP (strict definition): Metastatic neck lymphadenopathy where no primary tumour develops or is found within a subsequent 5-year follow-up period.

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2. Why Does CUP Happen?

Historical note: In 1882, Volkmann believed CUP arose from degeneration of a branchial cyst into carcinoma ("branchiogenic carcinoma") - but this theory has been largely abandoned. Martin et al. in 1950 set strict criteria to diagnose true branchiogenic carcinoma, which very few cases actually meet.

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3. Most Common Likely Primary Sites

1. Palatine tonsil - single most common occult primary site
2. Tongue base (lingual tonsil)
3. Nasopharynx
4. Pyriform sinus
5. Infrahyoid epiglottis

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4. Nodal Level and Likely Primary Site Correlation

Levels I-IV involvement is almost exclusively associated with upper aerodigestive tract SCC, with Level II being the most common.

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5. Role of HPV and EBV

HPV (Human Papillomavirus)

• p16 IHC positivity in the metastatic node reliably predicts oropharyngeal origin (tonsil or tongue base)
• Typical patient: middle-aged man, minimal smoking/alcohol history, cystic neck mass
• Often misdiagnosed as branchial cleft cyst - all lateral cystic neck masses in patients over 35 must be considered malignant until proven otherwise
• p16 positivity → perform bilateral tonsillectomy + lingual tonsillectomy (diagnostic AND therapeutic)

EBV (Epstein-Barr Virus)

• EBV serology positivity → strongly indicates nasopharyngeal primary
• EBV is the only tumour marker of clinical value in CUP

Under the current TNM (8th edition) staging: T0 category is only retained for HPV-associated oropharyngeal SCC and nasopharyngeal carcinoma (where viral testing can confirm the primary origin). For all other CUP cases, T0 is eliminated.

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6. Workup / Investigation Algorithm

Step 1 - History and Clinical Examination

• Heavy smoking/alcohol → primary outside nasopharynx
• Multiple sexual partners / orogenital contact → oropharyngeal primary (HPV-related)
• Fibreoptic nasolaryngoscopy with special attention to tongue base, nasopharynx, infrahyoid epiglottis, pyriform sinus

Step 2 - FNAC (First)

• Always get FNAC before imaging (to avoid PET-CT artefacts from prior biopsy)
• Confirms SCC histology
• Can test HPV (ISH + p16 IHC) and EBV on the aspirated material

Step 3 - Core Biopsy

• To assess HPV and EBV status if FNAC is non-diagnostic

Step 4 - Cross-sectional Imaging (CT and/or MRI)

• Identifies the primary in many cases
• MRI with diffusion sequences is increasingly useful

Step 5 - FDG PET-CT (KEY investigation)

• Must be done before any biopsy/EUA to avoid false positives
• NICE recommends considering PET-CT as the first imaging investigation
• Meta-analysis results:
  • FDG PET-CT: detects 31.4% more primary sites than conventional workup alone
  • Sensitivity 0.89, Specificity 0.73
  • Also detects occult distant metastases and synchronous cancers (lung, colorectal)
• If EBV positive on biopsy → targeted nasopharynx biopsy

Step 6 - EUA + Panendoscopy + Surgical Biopsies

• Panendoscopy (rigid pharyngolaryngoscopy)
• Bilateral tonsillectomy
• Tongue base mucosectomy (lingual tonsillectomy)
• Directed biopsies of nasopharynx, pyriform sinus, and any suspicious area
• Consider Narrow Band Imaging (NBI) endoscopy to highlight subtle mucosal abnormalities

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7. Modern Surgical Approaches to Find the Primary - TORS / TLM

Transoral Laser Microsurgery (TLM)

• Inspects all mucosal surfaces under high magnification
• Looks for subtle signs: pallor, neovascularity, corkscrew telangiectasia, papillary growth, mucosal friability
• Takes a "cut-surface view" biopsy - the laser cut surface of tumour is paler and drier than surrounding tissue
• Sends to frozen section; if positive → resects to negative margins

Results with TLM:

Transoral Robotic Surgery (TORS)

• Similar superior results to TLM
• Palatine + lingual tonsillectomy performed robotically
• Particularly powerful in p16-positive cases (89% detection rate in one series)

Key principle: If p16 IHC is positive on the neck node aspirate and nasopharyngoscopy is clear → go straight to transoral palatine + lingual tonsillectomy (it diagnoses AND treats the two most likely sites, avoiding wide-field pharyngeal radiotherapy)

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8. Treatment

ENT-UK MDT Treatment Guidelines Summary:

Surgical Management of the Neck

• N1 (no ECS): Selective neck dissection (SND) or surveillance alone after RT
• N2a-N2b: Selective neck dissection is valid (risk of level I and V metastasis is rare in CUP unless N3)
• N3 or ECS: MRND + adjuvant CRT
• "Violated neck" (prior open biopsy): Not a contraindication to good outcomes with current multimodal management

Radiation Therapy Controversy

• IMRT is the current standard - allows parotid gland sparing and significantly reduces xerostomia
• Total mucosal irradiation dose: 50 Gy in 25 daily fractions is adequate for occult disease control
• Nodal stage is the most important risk factor for local recurrence

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9. Prognosis and Patterns of Failure

Survival:

• Overall 5-year survival for all stages: 52-75%
• N1 disease: up to 100% 5-year survival
• N2-N3 disease: ~60% 5-year survival
• Recent series from Memorial Sloan Kettering (IMRT): 2-year regional progression-free survival 90%, OS 85%

Patterns of Failure:

• Primary site emergence: 0-66% (mainly in patients treated with surgery alone); usually occurs within 24 months, most often in the oral cavity, oropharynx, and nasopharynx
• Distant metastases: Occur within 1 year of treatment completion; lung is the most common site
• FDG PET-CT is the best method for detecting recurrence

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10. Key Summary Points (Quick Recall)

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Transoral Robotic Surgery (TORS) - Detailed ENT Textbook Review

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1. What is TORS?

The surgeon controls miniaturised articulated instruments and a high-definition 3D camera from a console away from the patient, achieving precision, stability, and visualization that is impossible with conventional transoral instruments.

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2. Historical Background

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3. The Robotic System Components

Key Instruments:

• 5 mm or 8 mm diameter interchangeable instruments
• Atraumatic forceps, monopolar cautery spatula (most common cutting/dissecting tool), bipolar cautery, dissectors
• 8.5 or 12 mm binocular stereoendoscopy camera - provides high-definition 3D visualization
• Fibre laser technology - now adaptable to robotic arms; more precise cutting, less thermal damage than monopolar cautery

Access to the Oropharynx:

• Feyh-Kastenbauer (FK) retractor - most common
• Crowe-Davis retractor
• McIvor retractor
• Dingman retractor

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4. Indications for TORS

FDA-Approved:

• T1-T2 oropharyngeal tumours (palatine tonsil, tongue base/BOT)

Commonly Used For:

1. Oropharyngeal SCC - most common application; tonsil and tongue base tumours
2. Supraglottic laryngeal cancer - supraglottic partial laryngectomy
3. Unknown primary - bilateral tonsillectomy + lingual tonsillectomy (diagnostic + therapeutic)
4. Parapharyngeal space tumours - benign salivary gland tumours, schwannomas, branchial cysts
5. Hypopharyngeal tumours - selected cases
6. Tongue base reduction for obstructive sleep apnoea (OSA)
7. Benign conditions - epiglottoplasty, vallecular cysts, Eagle's syndrome, posterior glottic pathology

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5. Contraindications

Absolute Contraindications (for oropharyngeal cancer):

• Inadequate transoral access / difficult mouth opening / trismus
• Incomplete tumour visualization despite spatulate retraction
• Deep extrinsic muscle invasion in tongue base tumours
• Invasion lateral to constrictor muscles into deep tissues
• Pre-vertebral fascia invasion
• Laryngeal involvement
• Retropharyngeal position of internal carotid artery (scans must be carefully studied)
• Tumour crossing the midline (BOT tumours)

For Parapharyngeal Space:

• Tumour adherent to or involving the carotid artery
• Vascular tumours (paragangliomas)
• Skull base bony involvement
• Malignant tumours of the parapharyngeal space
• Dumbbell tumours with significant parotid gland involvement

For Tonsil Tumours:

• Extension to parapharyngeal space and pterygoid musculature (relative contraindication)

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6. Pre-operative Assessment

1. Mouth opening and neck mobility - adequate access is essential
2. Cross-sectional imaging (CT/MRI) - assess tumour extent, confirm resectability, look for retropharyngeal carotid artery
3. PET-CT - staging, identify unknowns
4. HPV/p16 + EBV status - from FNAC of neck node
5. Dental review - for radiation planning if adjuvant RT planned
6. Anaesthetic assessment - airway, tracheostomy planning

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7. Surgical Technique

General Setup:

• Patient supine, neck extended, mouth propped with retractor
• Robot docked over the patient's head
• Surgeon at console (may be in same room or remote)
• Assistant at bedside with suction + haemostasis

For Tonsil Tumours (Radical Tonsillectomy):

1. Neck dissection performed first (same GA or prior sitting) - ipsilateral lingual and facial arteries are identified and ligated in continuity
2. Resection by monopolar cautery (laser if available)
3. En bloc removal - resection specimen is essentially a lateral oropharyngectomy including the constrictor muscle of the tonsil bed
4. Margins checked intraoperatively - areas of concern marked with methylene blue for pathologist
5. Further margins harvested if needed, especially at the inferior aspect where tonsil meets tongue base
6. Specimen orientated on a mount and sent for histology

For Tongue Base (BOT) Tumours:

1. Resectability confirmed on imaging
2. Midline crossing is a contraindication
3. Ipsilateral tongue base resection; further margins especially at deeper aspect of BOT
4. Specimen orientated and sent for histology

For Tumours Involving Both Tonsil and BOT:

• Cut through tonsil and constrictors ≥5 mm from tumour edge
• Leave cranial part of tonsil, resect tonsil tumour to styloglossus
• Then make BOT cuts and remove entire specimen en bloc

Principle:

TORS = En bloc resection with clear margins (unlike TLM which uses the "cut-through" piecemeal technique)

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8. TORS vs. Transoral Laser Microsurgery (TLM) - Key Comparison

The significant TLM literature paved the way for TORS to become established as a valid management of tonsil tumours with firm long-term oncological outcomes.

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9. Outcomes Data

Safety (Weinstein et al., multicentre prospective - 177 patients):

• No intra-operative mortality
• Average blood loss: 83 mL (no transfusions)
• Serious adverse events: 16% (required intervention)
• Tracheostomy at follow-up: 2.3%
• Gastrostomy tube dependence: 5%
• Positive margin rate: 4.3%

Survival (White et al., 89 patients, 2 institutions):

• 2-year recurrence-free survival: 86.5%
• None of the patients were gastrostomy-tube dependent at follow-up

Moore et al. (45 patients, T1-T4a, prospective):

• All margins negative
• All tracheostomized patients eventually decannulated
• All feeding tube patients eventually had tubes removed

Recent Meta-Analyses (2024-2026):

• Gupta et al., 2024 (PMID 38795678) - Quality of life comparing TORS vs. primary radiotherapy: similar QOL outcomes, supporting TORS as a valid alternative
• Cheung et al., 2026 (PMID 41521853) - Oncologic outcomes in HPV-associated OPSCC: strong results confirming TORS efficacy in HPV+ disease

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10. TORS for Specific Sites

A. Oropharyngeal Cancer (Most Common Application)

• Tonsil SCC and tongue base SCC (T1-T2, FDA-approved)
• HPV-positive OPSCC: TORS + selective neck dissection ± de-escalated adjuvant RT
• Goal: avoid or de-intensify chemoradiotherapy → reduce long-term xerostomia, dysphagia, feeding tube dependence

B. Supraglottic Larynx

• Supraglottic partial laryngectomy via TORS
• Avoids tracheostomy in many patients
• Functional preservation of voice and swallowing

C. Unknown Primary (CUP)

• Bilateral palatine tonsillectomy + lingual tonsillectomy
• Increases primary detection from 17-40% (traditional EUA) to 89-94%
• If p16 positive: TORS tonsil/tongue base surgery is both diagnostic AND therapeutic, eliminating the need for wide-field pharyngeal RT

D. Parapharyngeal Space

• Ideal candidates: Benign pre-styloid salivary gland tumours, schwannomas, branchial cysts
• Tumour must displace carotid posteriorly/laterally (not medially)
• Avoids the traditional transcervical or transparotid approach
• No external scar

E. Obstructive Sleep Apnoea (OSA)

• Tongue base reduction (lingual tonsillectomy) to reduce retrolingual obstruction
• First prospective study on single-port robotic tongue base resection for sleep apnoea reported 2025

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11. Post-operative Care

• All patients managed in HDU overnight - for airway monitoring and oral bleeding observation
• Usually extubated after surgery; no routine need for prolonged intubation or tracheostomy
• Oral diet protocol:
  • Day 0: Nil by mouth
  • Day 1: Clear fluids
  • Day 2: Free fluids
  • Day 3+: Soft diet → normal diet

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12. Complications

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13. Ongoing Trials and Evidence Base

No randomized trials yet directly comparing TORS to chemoradiation as primary treatment, but multiple Phase II/III trials are underway.

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14. Recent Advances and Future Horizons (2024-2026)

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15. Key Summary Points

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