Necrotic Features in Post‐Radiation Nasopharyngeal Biopsies Associated With Carotid Blowout

Objectives Post‐radiation nasopharyngeal biopsies in patients with nasopharyngeal carcinoma (NPC) are primarily performed to exclude recurrence, yet their utility in assessing radiotoxicity remains underexplored. This study characterizes two distinct histological patterns of necrosis: coagulative stromal necrosis (Type A) and microscopic osteoradionecrosis (ORN; Type B). We aim to analyze the association of these patterns with radiotherapy (RT)‐related complications. Methods Data from a cohort of 483 patients were reviewed. Study groups included Type A ( n = 30), Type B ( n = 12), and clinically diagnosed skull base osteoradionecrosis (cORN, n = 25). Controls were categorized by histological findings: ulcer ( n = 24), fibrosis ( n = 43), and viable lymphoid tissue ( n = 21). A comparison cohort of patients without posttreatment biopsy ( n = 63) was also included. Results Carotid blowout syndrome (CBS) occurred exclusively in the study groups: Type A (13.3%), Type B (8.3%), and cORN (12.0%). No CBS events were observed in the histological control groups or the comparison cohort. Notably, Type A biopsies were temporally clustered closely with CBS events, specifically occurring from 3 months before to 1 month after the episode. Conclusion Type A and Type B histological patterns are associated with an increased risk of carotid blowout, comparable to cORN. Type A may represent a “two‐hit” necrotic transition from a vulnerable fibrotic substrate. Beyond diagnosing recurrence, post‐RT biopsies may offer valuable insights into the status of deep tissues. Identifying these patterns can aid in risk stratification and potentially facilitate early intervention to mitigate severe complications. Level of Evidence 4.