Introduction: Local recurrence of prostate cancer (PCa) following radiotherapy may be treated with curative intent using salvage highintensity focused ultrasound (s-HIFU). The interpretation of needle core biopsy specimens following s-HIFU is a daunting task, even for experienced pathologists. We describe various histopathological features encountered in biopsy specimens following whole-gland s-HIFU in one of the largest descriptive studies to date. Methods: Fifty-five patients with biopsy-proven localized radiorecurrent PCa underwent s-HIFU and transrectal ultrasound (TRUS)- guided prostatic needle biopsies at 180 days post-treatment. All biopsies were reviewed by two genitourinary pathologists. Results: PCa was detected in 11 (24%) biopsies. Radiation therapyassociated changes were identified in all cases. Additional findings included extensive coagulative stromal necrosis (100%), smudgy chromatin of cancer nuclei (82%), and markedly enlarged bizarre nuclei in the residual cancer (55%). Gleason grade assignment was possible in 10 (91%) of these biopsies and concordance of Gleason grading between pre- and post-therapy specimens was observed in six (60%) cases. Conclusions: The histological interpretation of needle biopsies following salvage HIFU is challenging and requires an understanding of the histopathological changes associated with this procedure in both tumoural and non-tumoural prostatic tissue. Accurate interpretation of the morphological changes following s-HIFU is instrumental for optimization of clinical decision-making and treatment planning in recurrent PCa.
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