The investigation of thyroid nodules is limited by the fact that up to 49% of the fine needle aspirations (FNA) performed are of "indeterminate cytological signification". Moreover, no fully reliable molecular marker for thyroid cancer have been described. The goal of this project is to study the expression of a specific kind of protein convertase in benign and in malignant thyroid nodules to determine its potential as a biomarker.

Patients that underwent thyroidectomy at the CIUSSS de l'Estrie-CHUS will be recruited and classified according to the pathological diagnosis. An immunohistochemistry technique, developed and calibrated for the specific protein convertase studied, will be undertaken. Results will be interpreted by a specialized pathologist.

Inclusion Criteria:

• Men of women, aged 18-100 y.-o.
• History of subtotal or total thyroidectomy at the "Centre intégré universitaire de santé et de services sociaux de l'Estrie - Centre hospitalier universitaire de Sherbrooke" (CIUSSS de l'Estrie - CHUS) between January 2010 and May 2016.

Exclusion Criteria:

• Refusal to participate to the study.
• Unavailability of the formalin-fixed, paraffin-embedded tissues.
• Uncertain pathological diagnosis.

Patients from the territory of the CIUSSS de l'Estrie - CHUS, that underwent a subtotal or total thyroidectomy