When persistent idiopathic facial pain is not idiopathic: Facial pain attributed to lung cancer and comparative review of classification systems

OBJECTIVE: Facial pain attributed to lung cancer (FPLC) is frequently misclassified as persistent idiopathic facial pain (PIFP). This study reviewed published cases, retrospectively applied existing criteria for PIFP to evaluate misclassification, characterized clinical features of FPLC, and proposed a diagnostic framework. METHODS: A structured search of MEDLINE, Embase, and Web of Science through December 13, 2025, identified 51 English-language case reports of orofacial or pharyngeal pain secondary to lung cancer. Thirty-three cases contained sufficient detail to allow retrospective application of PIFP criteria from leading classification systems. RESULTS: Twenty-seven cases, 81.8%, met criteria for PIFP despite an underlying malignancy. Adding a requirement to exclude systemic disease substantially reduced misclassification. The proposed diagnostic criteria for FPLC demonstrated an 87.9% diagnostic accuracy. CONCLUSION: Idiopathic orofacial pain phenotypes overlap with FPLC. Excluding systemic causes improves the diagnostic validity of classification systems. The consistent clinical profile of FPLC supports the use of defined diagnostic criteria.