Oropharynx squamous cell carcinoma

• Asymmetric soft tissue mass with contrast enhancement in the oropharynx (tonsil, base of tongue, or soft palate most common)
• Regional lymph node involvement—particularly level II nodes—with short-axis diameter >10 mm, loss of fatty hilum, or cystic change
• Signs of extracapsular extension: loss of adjacent fat planes, irregular capsular enhancement, or ill-defined margins

• CT shows asymmetric soft tissue mass with heterogeneous contrast enhancement arising from the oropharynx, with the tonsil, base of tongue, and soft palate being the most common sites of origin.
• In advanced disease, there is loss of normal fat planes as the tumor extends beyond its site of origin into adjacent structures, indicating local invasion.
• Metastatic lymph nodes typically demonstrate short-axis diameter greater than 10 mm, asymmetry, and loss of normal fatty hilum; cystic change or central necrosis may be present.
• HPV-associated OPSCC (p16-positive) shows high propensity for early and extensive nodal metastasis, particularly within the level II nodal station—level II involvement is the most common metastatic site from p16-positive OPSCC.
• Extracapsular extension is identified by loss of adjacent fat planes, irregular or spiculated capsular enhancement, and ill-defined nodal margins, indicating high-risk disease.
• The lingual surface of the epiglottis is excluded from OPSCC staging and considered laryngeal; the nasopharyngeal surface of the soft palate is considered nasopharyngeal for staging purposes.
• HPV-positive and HPV-negative OPSCC have markedly different staging criteria (per 2017 AJCC 8th edition) and dramatically different prognoses (90% versus 40% 5-year survival, respectively).
• Careful assessment of neck lymph nodes is essential as nodal status is a critical prognostic and treatment-planning factor, with particular attention to level II nodes in suspected HPV-positive disease.

• Benign tonsillitis or tonsillar hypertrophy—lacks enhancement, preserves normal architecture, typically symmetric, and patients lack constitutional symptoms or weight loss
• Lymphoma involving Waldeyer ring—typically demonstrates more symmetric bulky nodal disease, less associated mass effect, and different imaging characteristics on imaging
• Nasopharyngeal carcinoma—arises superior to the soft palate and involves the nasopharynx rather than oropharynx proper; staging and prognosis differ significantly
• Adenocarcinoma of minor salivary glands—typically lacks the aggressive nodal involvement pattern and may show different enhancement characteristics
• Non-metastatic reactive lymphadenopathy—nodes remain <10 mm in short axis, maintain central fatty hilum, and lack enhancement irregularities or cystic change

Clearly specify the anatomical site of the primary tumor (tonsil, base of tongue, or soft palate), describe the size and enhancement pattern of the mass, meticulously characterize all lymph nodes (particularly level II) with short-axis diameter, features of nodal involvement (hilum loss, cystic change), and presence or absence of extracapsular extension—noting that level II nodal involvement strongly suggests HPV-positive disease.

• Mistaking reactive lymphadenopathy or benign tonsillar hypertrophy for malignancy—measure short-axis diameter carefully and assess for enhancement, loss of hilum, and ancillary features of malignancy
• Underestimating the significance of level II nodal involvement—its presence should strongly suggest HPV-positive OPSCC and warrants comprehensive description of nodal characteristics for treatment planning
• Failing to identify extracapsular extension on imaging—this high-risk feature is critical for prognosis and treatment intensity selection and requires careful assessment of fat planes and capsular margins
• Incorrectly staging nasopharyngeal or laryngeal tumors as OPSCC—remember that the nasopharyngeal surface of the soft palate belongs to the nasopharynx and the lingual surface of the epiglottis belongs to the larynx for staging purposes