In this case presentation, a 19-year-old male patient was examined because of complaints of right lateral chest swelling, lateral pain, and high fever at night. After a chest CT, the patient was directed to our clinic with a pre-diagnosis of chest wall tumor following the detection of peripheral consolidation concurrent with atelectasis in the lower lobe lateral basal segment in the right lung and a lesion with irregular contour in pleura and the thoracic wall, starting at this level and descending to the inferior. Because the symptoms pointed to infection, antibiotic therapy was started and a fine-needle aspiration biopsy was concurrently performed. Results of the biopsy were reported as "suspicious cytology." The patient, who responded to antibiotic therapy both clinically and radiologically, expectorated a foreign body during monitoring. Pathological examination reported "in herbal quality, grass inflorescence" as the traits of the expectorated body. In the literature there are cases in which grass inflorescence, in accordance with its nature, passed distally out of the chest wall with migration following the aspiration. However, no other publication has reported an intriguing case such as ours, in which the grass inflorescence caused inflammation that mimicked a chest wall tumor and then was expectorated moving in the opposite direction.