Post-traumatic Pleomorphic Adenoma of the Scalp: A Case Report and Proposal for Updated Diagnostic Criteria for Trauma-related Neoplasia

OBJECTIVE: Pleomorphic adenomas classically arise from salivary gland epithelial tissue and may occur after trauma. Criteria for establishing trauma-tumor causation are outdated. This case presents a patient with two separate post-traumatic pleomorphic adenomas and proposes updated criteria for evaluating trauma-related tumor causation. METHODS: A 59-year-old presented with a frontotemporal scalp lesion one year after workplace head trauma. Nine years earlier she underwent parotidectomy of a pleomorphic adenoma following jaw trauma. RESULTS: The excised scalp lesion was a benign mixed tumor of skin. Histopathologic differences between the scalp and parotid lesions established them as separate primary tumors. The case was evaluated for causation during a workers' compensation claim. DISCUSSION: The case demonstrates a rare occurrence of multiple post-traumatic benign mixed tumors. We propose an updated and comprehensive set of criteria for objectively assessing trauma-tumor causation.