(TC09) End-O The Rainbow – Understanding the Relationship between Clinical Appearance and Histologic Findings of Biopsy from Apical Periodontitis – A Photo and Histology Demonstration

Persistent apical periodontitis often necessitates endodontic surgery, with accurate diagnosis relying on microscopic analysis by oral pathologists. For instance, periapical granulomas - the most common periapical lesion of endodontic origin - are identified histologically by the presence of connective tissue, blood vessels, and inflammatory cells. In contrast, radicular cysts are confirmed by the presence of cavitation and an epithelial lining, and may sometimes contain cholesterol crystals surrounded by neutrophilic leukocytes and foreign-body giant cells within the cyst wall. Periapical actinomycosis, another relevant endodontic lesion, is distinguished histologically by “sulfur granules” that are characteristically associated with Actinomyces species and Propionibacterium propionicum. Occasionally, biopsies submitted as suspected periapical granulomas or cysts are diagnosed as odontogenic keratocysts, the most common non-endodontic periapical lesion that mimics endodontic pathosis. The objective of this table clinic is to showcase various high-resolution clinical images of periapical tissue specimens collected during periapical surgery from patients diagnosed with apical periodontitis. Specimens were categorized based on their macroscopic color appearance: 1) yellow, indicating cholesterol in cysts, 2) green/yellow, suggesting actinomycosis, 3) red, associated with granulomas, and 4) white, reflecting odontogenic keratocysts. Corresponding histological slides will highlight key histological features such as 1) cholesterol or cholesterol crystals, 2) “sulfur granules”, 3) granulation tissue, and 4) keratinaceous debris. By illustrating various macroscopic colors of periapical tissue biopsies, this table clinic aims to provide valuable preliminary insights regarding the histopathological composition of these periapical specimens. A thorough understanding of these correlations will aid clinicians in initial biopsy assessments and appropriate treatment planning.