Unusual pulmonary vascular lesions after intravenous injections of microcrystalline cellulose

Summary We present the morphological features of a case of fatal pulmonary granulomatosis from illicit intravenous injections of microcrystalline cellulose derived from pentazocine tablets. Extensive foreign body granulomas were found in the lumena and walls of pulmonary vessels and in the pulmonary interstitium. Previously unreported gaps containing foreign material were found in the walls of medium-sized muscular pulmonary arteries. This peculiar finding is discussed in the light of the possible mechanisms involved in the removal of embolized foreign material.