Subcutaneous and Intraperitoneal Lipogranulomas Following Subcutaneous Injection of Olive Oil in Sprague-Dawley Rats

Olive oil is commonly employed as a solubilizing agent for lipophilic materials in preclinical studies in rodents. Here we report that following subcutaneous (SC) injection of olive oil to Sprague-Dawley (SD) rats, local SC lipogranulomas formed, which were associated with an unusual location of the same changes in the peritoneum. Macroscopically, multifocal white spots were found over the liver and mesentery. Histologically, lipid granulomas were seen in the SC injection site, as well as on the capsular or serosal surface of the abdominal organs. No abnormal clinical signs were noted except for swelling at the injection site. The olive oil may have reached the peritoneal cavity from the SC tissue passively via the lymphatic vessels or actively after engulfment by antigen-presenting cells via the lymphatic or blood vessels. These findings are of particular importance for drug safety assessments, as the occurrence of lipogranulomas in locations distant from the site of administration may lead to misinterpretation of histological results. We suggest that these aberrations may be induced by the administration of olive oil as a vehicle.