This observational study will evaluate whether salivary interleukin-6 levels and selected interleukin gene polymorphisms are associated with regional lymph node involvement in patients with oral squamous cell carcinoma.

Adult patients with histologically confirmed oral squamous cell carcinoma will be enrolled before receiving any cancer-specific treatment. Participants will be classified into two groups according to the presence or absence of regional lymph node metastasis: OSCC N0M0 and OSCC N+M0.

The study does not involve any experimental treatment and does not change the standard diagnostic or therapeutic pathway. Each participant will provide a saliva sample using a sterile absorbent swab. The saliva sample will be used to measure interleukin-6 levels. Available biological material will also be used to analyze selected interleukin gene polymorphisms, including IL6, IL1B, IL10, IL8/CXCL8, and IL1RN.

The aim of the study is to explore whether these salivary and genetic markers may help characterize different biological patterns of locoregional progression in oral squamous cell carcinoma.

Oral squamous cell carcinoma is characterized by variable biological behavior, including different patterns of regional lymph node involvement. Regional lymph node metastasis is one of the main prognostic factors in this disease. However, patients with similar clinicopathological characteristics may show different patterns of locoregional progression, suggesting that additional biological markers may help describe tumor behavior.

This multicentre observational cross-sectional study will investigate salivary interleukin-6 and selected interleukin gene polymorphisms in adult patients with histologically confirmed oral squamous cell carcinoma. Participants will be enrolled before any cancer-specific treatment and classified according to regional lymph node status as OSCC N0M0 or OSCC N+M0.

Saliva will be collected using a standardized sterile absorbent swab procedure. Salivary interleukin-6 levels will be quantified and expressed as pg/mL. Selected interleukin-related genetic polymorphisms, including IL6, IL1B, IL10, IL8/CXCL8, and IL1RN, will be analyzed from available biological material using validated molecular biology methods.

The primary objective is to compare salivary interleukin-6 levels between patients without regional lymph node metastasis and patients with regional lymph node metastasis. Secondary objectives include evaluating the association between nodal status and interleukin gene polymorphisms, and exploring the relationship between these polymorphisms and salivary interleukin-6 levels.

No experimental treatment will be administered, and participation will not modify the standard diagnostic or therapeutic management of oral squamous cell carcinoma.

Inclusion Criteria:

• Age 18 years or older
• Histopathologically confirmed diagnosis of oral squamous cell carcinoma of the oral cavity
• Oral squamous cell carcinoma site excluding oropharyngeal sites
• Defined regional lymph node status allowing classification as OSCC N0M0 or OSCC N+M0
• Absence of distant metastasis, classified as M0
• Saliva sample collection feasible before any OSCC-specific oncological treatment, including surgery, radiotherapy, chemotherapy, immunotherapy, or targeted therapy
• Suitability for saliva collection using a standardized absorbent swab
• Availability of biological material for genotyping
• Ability to provide written informed consent for study participation, biological sampling, and genetic analysis

Exclusion Criteria:

• Age younger than 18 years
• Oral squamous cell carcinoma involving oropharyngeal sites
• Presence of distant metastasis
• Previous OSCC-specific oncological treatment before saliva sample collection
• Acute infection at the time of sampling or within the previous 2 weeks
• Active or inadequately controlled systemic autoimmune or inflammatory disease that may significantly alter cytokine profiles
• Systemic immunosuppressive or immunomodulatory therapy within the previous 4 to 8 weeks
• Recent oncological treatment for malignancies other than OSCC within the previous 6 months, if considered potentially interfering with the immune-inflammatory profile
• Clinically significant acute oral infection or inflammatory process at the time of sampling
• Active oral bleeding or evident blood contamination of the salivary swab Invasive dental procedures within the previous 2 weeks
• Systemic antibiotic therapy within the previous 2 weeks
• Inability to provide written informed consent

The study population will include adult patients with histopathologically confirmed oral squamous cell carcinoma of the oral cavity, enrolled before any OSCC-specific oncological treatment. Participants will be classified according to regional lymph node status into two observational cohorts: OSCC N0M0, defined as absence of regional lymph node metastasis and absence of distant metastasis, and OSCC N+M0, defined as presence of regional lymph node metastasis and absence of distant metastasis. Patients will be recruited from participating Italian study centres involved in the clinical management of oral squamous cell carcinoma.

Data will be available upon motivated request to the corresponding authors.