Extranodal extension (ENE) refers to the spread of head and neck squamous cell carcinoma (HNSCC) outside the lymph nodes. It is a well-known factor that indicates a poorer prognosis and outcome for patients who have undergone surgical removal of the cancer. In such cases, it is recommended to combine chemotherapy with radiation therapy after surgery.

As the number of cases of HNSCC related to the human papillomavirus (HPV) is increasing, treatment approaches have shifted towards using radiation therapy as the primary treatment method instead of surgery. This raises an important question about the significance of ENE observed through imaging tests (referred to as iENE) and its impact on the prognosis. Unfortunately, this question remains unanswered.

The objective of this project is to conduct a comprehensive study across multiple medical institutions. The investigators will gather data including scan results, histopathology reports, and data from patient charts from individuals who have been treated for head and neck cancer. The aim is to analyze and correlate the findings between the pathological evidence of ENE and the imaging results, while also assessing the prognostic value of iENE. Additionally, the investigators will explore the influence of HPV status on these factors.

By collecting and analyzing this data, the investigators hope to establish standardized criteria that can assist radiologists in accurately identifying ENE through imaging tests. This research is essential for enhancing our understanding of HNSCC and improving the effectiveness of diagnostic procedures and treatment planning.

Inclusion Criteria:

The investigators will examine data from consecutive patients at each site treated between 1/1/1999 and 12/31/2020. Patients must fulfil all these criteria:

i. Been treated for oral cavity, oropharyngeal, carcinoma of unknown primary, laryngeal, or hypopharyngeal squamous cell carcinoma and be over the age of 18.

ii. The participants must have been treated with curative intent via surgery, radiotherapy, or chemoradiotherapy or a combination within the study inclusion period.

iii. The participants must have had CT or/and MRI scans of the neck, performed within 12 weeks before the start of treatment.

iv. Results for the presence or absence of extranodal extension on CT or/and MRI scans, or ability to report them within the deadline period.

v. For surgically-treated patients: Results for the presence or absence of both extranodal extension on histopathology and on radiology, or ability to report them within the deadline period.

vi. Must have had at least two years of follow-up, or death. vii. Data on staging must be available at least in TNM 7th edition or later editions.

Exclusion Criteria:

i. Patients who were diagnosed with distant metastasis at presentation. ii. Patients treated palliatively at first presentation iii. Patients presenting with recurrent disease who don't meet all the eligibility criteria above

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Patients presented and treated for Head and neck squamous cell carcinoma

The data will bill kept in the HNCIG database, and might be shared with other researchers following a reasonable request (and following agreement by the HNCIG board)