Longitudinal pilot study examining the effect of punch biopsy on equine sarcoid growth dynamics

Background: Nonexcisional tissue biopsies facilitate pre-operative confirmation of equine sarcoid yet fear of lesion deterioration currently limits its use in the diagnostic workup.Objectives: To evaluate the effect of a single punch biopsy on tumour growth dynamics [thickness, area, circumference, viral load (VL) and Visual Analog Scale (VAS)].Animals: Six client-owned horses with 11 sarcoids of various classification.Materials and Methods: Growth dynamics were recorded on a weekly basis, 12 weeks pre- and 24 weeks post-biopsy. The effect of a single punch biopsy on growth dynamics was estimated by linear mixed-effect models. Spearman's rank correlation coefficient (SRCC) was calculated to investigate correlations with the number of weeks before and after the intervention.Results: While statistically significant post-biopsy changes were recorded for all parameters except VL, no parameter was consistently increased after the biopsy intervention. In two of 11 sarcoids, the VL correlation pattern revealed significant strong correlations: sarcoid 6 (pre: r = -0.66, p < 0.05; post: r = 0.81, p < 0.001), increased VL; and sarcoid 8 (pre: r = 0.85, p < 0.001; post: r = 0.17, p > 0.05), no further increase after biopsy.Conclusions and Clinical Importance: Our results indicate that post-biopsy lesion deterioration is not a general concept that applies to all sarcoids, and both deterioration or improvement are possible outcomes over a 24-week period. Further clinical studies with a larger sample size are needed before a definitive conclusion can be made.