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A recurrent sore throat can occur in a number of pathologies. Most often it is as a result of some local pathology like Rhinosinusitis, nasopharyngitis, tonsillitis, GERD (gastroesophageal reflux disease), LPR (laryngopharyngeal reflux). Rather than relapsing and recurring course malignancies tend to have a progressive course. Further age is a crucial factor.
Younger people usually do not have malignancies. Your doctor must have checked your throat, and he would for sure have picked something if there was any such thing. GERD and LPR are mainly known to cause recurrent sore throat. Malignancy is the last thing one would suspect at your age.