This week's case was donated by Dr. Neil Harris and Dr. Stacy Beal. The patient is an infant with a history of tracheobronchomalacia and "eosinophilia" on prior bronchoscopy. A routine complete blood count was negative without evidence of peripheral eosinophilia. The following structures were seen on a Giemsa-stained bronchoalveolar lavage specimen using the 100x objective. They have a diameter of 1-3 micrometers. Identification?