A descriptive histopathological framework for radiotherapy-related muscle injury in salvage surgery for hypopharyngeal cancer

BACKGROUND: Radiotherapy-related normal tissue injury is clinically important in salvage surgery for hypopharyngeal cancer, but its histopathological features in clinical specimens remain poorly defined. AIMS/OBJECTIVES: To propose a practical descriptive histopathological framework for radiotherapy-related muscle injury using salvage surgical specimens. MATERIAL AND METHODS: We retrospectively examined anterior cervical muscle specimens obtained during salvage total pharyngolaryngectomy after definitive radiotherapy or chemoradiotherapy. Two head and neck surgeons with postgraduate training in pathology independently reviewed H&E-stained sections without reference to treatment exposure and, after discussion, established a four-tier semiquantitative framework based on recurring morphologic patterns. A board-certified head and neck pathologist subsequently reviewed all specimens blinded to treatment exposure and clinical information. No statistical comparison between treatment groups was intended. RESULTS: Thirteen previously irradiated patients and two non-irradiated controls were included. Irradiated muscles showed a spectrum of changes ranging from mild myofiber swelling and atrophy to rupture, fibrosis, necrosis, and scarring. Non-irradiated controls showed preserved muscle architecture. CONCLUSIONS AND SIGNIFICANCE: This study proposes a practical descriptive framework for radiotherapy-related muscle injury in salvage surgery. The grades should be interpreted as predominant morphologic patterns rather than rigid chronological stages or statistically validated treatment-specific categories.