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Squamous Cell Carcinoma of Maxillary Sinus: AJCC Classification & Investigations

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PART I: AJCC (8th Edition) TNM Classification - Maxillary Sinus

T (Primary Tumour) Classification

Note: T4a = resectable, moderately advanced; T4b = unresectable, very advanced

N (Regional Lymph Nodes) Classification

ENE = extranodal extension. Recognition of ENE as an upstaging factor is a key update in the 8th edition.

M (Distant Metastasis) Classification

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Overall Stage Grouping

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Historical Staging Reference: Ohngren's Line

• Infrastructural (antero-inferior to the line): earlier presentation, better prognosis, more amenable to complete resection
• Suprastructural (superior and posterior to the line): later presentation, involves critical structures (orbit, skull base, carotid), poorer prognosis

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PART II: Investigations to Stage and Diagnose Maxillary Sinus SCC

A. Clinical Assessment

1. Full history - onset, nasal obstruction, epistaxis, facial pain/swelling, cheek numbness, diplopia, trismus, loose teeth, epiphora (each symptom maps to a specific direction of spread)
2. Head and neck examination
   • Inspection: facial swelling/asymmetry, orbital proptosis, palate bulge
   • Palpation: cervical lymphadenopathy (levels I-III are most relevant), cheek/infraorbital thickening
3. Cranial nerve examination - CN II, III, IV, V1, V2, VI palsy indicates advanced disease (orbital apex/cavernous sinus involvement)
4. Oral cavity examination - palatal bulge or ulceration, loose teeth, widened alveolar ridge

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B. Endoscopic Evaluation

1. Rigid nasal endoscopy (0° and 30° telescopes)
   • Mandatory in all suspected cases
   • Assesses medial wall erosion, nasal cavity involvement, middle meatus extension
   • Identifies polypoid/ulcerative mass, assesses accessible biopsy sites
   • Note: outpatient biopsy may be non-diagnostic; tumour may show polypoid surface reaction

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C. Imaging Investigations

Primary Imaging (Both Required Together)

1. Contrast-enhanced CT scan (axial + coronal reconstruction)
   • Modality of choice for bony detail
   • Assesses: bony erosion/destruction of antral walls, posterior wall, hard palate, pterygoid plates, orbital floor
   • Detects: calcification, opacification, extent of bony involvement, skull base integrity
   • Evaluates: sinus walls, lamina papyracea effacement, teeth/alveolar involvement
   • Guides: surgical planning, custom prosthetic fabrication
2. Contrast-enhanced MRI (Gd-enhanced T1 + T2 + DWI sequences)
   • Superior for soft tissue assessment
   • Detects: dural/cerebral infiltration, orbital invasion, perineural spread
   • T2 sequences: distinguishes retained secretions from active tumour
   • Diffusion-weighted imaging (DWI): helps characterize lesion nature
   • Gadolinium-enhanced images: show tumour vascularity (flow voids), dural enhancement
   • 94-98% correlation with surgical findings

CT + MRI together are the standard - each is insufficient alone. (Scott-Brown's; Cummings Otolaryngology)

Additional Imaging

1. PET-CT (18-FDG)
   • Role: detecting distant metastases in pretreatment staging
   • Helps exclude occult metastatic disease and identify an unknown primary
   • Limited by: 18-FDG uptake by sinonasal inflammation (confounds interpretation of primary)
   • Useful in: posttreatment surveillance for recurrence
2. Chest X-ray / CT chest
   • Screening for pulmonary metastases
   • CT chest preferred for advanced (T3-T4) disease
3. CT/MRI of neck - for nodal staging (levels I-III principally)
4. Arteriography (selective, not routine)
   • Only if pre-operative embolization is being considered for highly vascular tumours

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D. Tissue Diagnosis

1. Biopsy - mandatory before any treatment
   • Transnasal endoscopic biopsy (most common)
   • Preferred under general anaesthesia - reduces non-diagnostic rate, allows biopsy from within sinus
   • Caldwell-Luc approach should be avoided if it would seed tumour or compromise subsequent resection
   • Facilities for haemorrhage control must be available (some sinus tumours are highly vascular)

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E. Laboratory Investigations

1. Full blood count (FBC/CBC) - baseline haematological status
2. Liver function tests (LFTs) - hepatic metastases screening
3. Renal function tests - pre-treatment baseline (especially if chemotherapy planned)
4. Serum electrolytes and coagulation profile - pre-operative baseline
5. Alkaline phosphatase / bone profile - bone metastasis screen

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F. Assessment Under General Anaesthesia (EUA)

1. Examination under anaesthesia (EUA) with endoscopy
   • Allows thorough examination of the nasal cavity, nasopharynx, post-nasal space
   • Enables representative deep biopsy from within the sinus
   • Assesses full extent of visible tumour, palate, and nasopharyngeal involvement

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G. Ophthalmological and Special Assessments

1. Formal ophthalmology assessment
   • Baseline visual acuity, extraocular movements, visual fields
   • Required when orbital involvement is suspected (guides decision on orbital exenteration)
2. Dental assessment/Orthopantomogram (OPG)
   • Bone involvement of alveolus/dentition
   • Pre-operative dental state for prosthetic planning
3. Audiometry - if Eustachian tube involvement is suspected (indicates advanced disease)
4. Neuroimaging/Neurosurgical consultation - if intracranial extension is suspected (T4b)

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Summary: Investigations at a Glance

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• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Tables 7.2, 7.3 (AJCC TNM Classification)
• Cummings Otolaryngology Head and Neck Surgery, Chapter 94 (Staging, Imaging, Biopsy, Workup)
• K.J. Lee's Essential Otolaryngology, Rhinology chapter (Ohngren's line, treatment concepts)
• Bailey & Love's Short Practice of Surgery, 28th Ed. (AJCC 8th edition staging principles)