Squamous cell carcinoma of the VADS represents the majority of cancers in ENT. Metastatic lymph node involvement is an important prognostic factor. In N0 patients clinically and scanographically, the prevalence of cervical lymph node metastasis remains important. Only the anatomopathological analysis of cervical lymph node dissection confirms the presence of a micro-metastasis. However, new criteria of interpretation in nuclear medicine seem promising in the detection of lymph node lesions not detectable in traditional imaging.

The main objective of this study is to study the positive predictive value (PPV) of CT scans in the anatomo-pathological analysis of N0 clinical and radiological or N + unilateral neck ganglia in patients with squamous cell carcinoma of the oral cavity.

The main objective is to study the positive predictive value of PET-CT in the identification of infra-clinical lymph node lesions for cancers of the oral cavity classified N0 or N + unilateral

Patients are admitted to ORL or maxillofacial consultation with initial clinical examination according to current recommendations (tumor evaluation, cervical palpation, locoregional examination).

A dated and signed diagram of the lesion and ganglionic areas will be made during this consultation.

A biopsy for histopathological examination of the lesion will be necessary to confirm the diagnosis of squamous cell carcinoma with P16 analysis. It will be performed during the consultation under local anesthesia if the lesion is accessible or under general anesthesia during panendoscopy.

All patients will benefit from an assessment of locoregional extension by CT cervicofacial and thoracic injected (in order to look for possible pulmonary metastases or suspicious mediastinal lymphadenopathies) as requested in the oncological recommendations and PET-CT. As part of the extension assessment, a panendoscopy or bronchial fibroscopy and gastro-oesophageal failure will be performed if risk factors ethanolotagagic are present.

If the lesion is not accessible for a biopsy during the inclusion visit, the patient is summoned for a panendoscopy. It is an examination under general anesthesia to make a biopsy of the primary tumor and to search for the absence of synchronous localization. In current practice, this examination requires overnight hospitalization.

The patient will be reviewed by the ORL or maxillofacial surgeon in consultation after receiving the anatomopathological findings of the lesion and the entire extension assessment (CT cervico-thoracic injected and PET-CT).

On CT PET, an analysis with additional interpretation criteria will be performed (SUVmax, SUV peak, MTG) on the primary tumor and on the invaded lymph nodes. A ganglion is considered invaded when its SUV is suppressed at 30% of the SUV of the original lesion.

The patient's file will have been previously presented in a Multidisciplinary Concertation Meeting, whose treatment will consist of a surgical excision of the primary lesion and a lymph node dissection.

The patient will be seen again in consultation at 10 days of his intervention as part of the follow-up postoperative in order to be able to receive all the anatomopathologic results of the operative specimen and ganglion dissection. The patient's record will have been represented in CPR in order to decide whether or not to have an adjuvant treatment based on the anatomopathological characters (capsular rupture, number of ganglions invaded, peri-nervous sheath).

Inclusion Criteria:

• 1st localization of squamous cell carcinoma of the oral cavity.
• Any tumor T according to the 2017 classification, N0 clinical and radiological or N + unilateral, M0
• Not challenged for tumor resection surgery and bilateral dissection.

Exclusion Criteria:

• age <18 years
• opposition of the curator concerning the person under guardianship
• subject under guardianship or deprived of liberty
• antecedent treatment of cancer of the upper aero-digestive tract (surgery, radiotherapy, chemotherapy)
• any current treatment for another cancer site

The population selected is that of any patient with squamous cell carcinoma of the oral cavity classified N0 clinical and radiological or unilateral N +, M0, not challenged for tumor resection surgery and bilateral cervical dissection. They will benefit in their assessment of extension of a PET-CT.

Patients will be selected during an ENT or maxillofacial consultation. They will receive clear and appropriate information from the study. They will decide whether to participate in the study.