A 34-year-old man without symptoms was referred to our hospital to clarify an abnormal chest radiograph showing a nodular pulmonary lesion. He was currently without symptoms, but had been treated two years prior for tuberculosis after presenting with mild fever, nonproductive cough, and a five-pound weight loss. There were no comorbidities and the patient denied a history of smoking. Physical examination revealed no abnormalities.
The chest radiography revealed a well-circumscribed mass in the left lung. CT scans demonstrated a mass with irregular borders, measuring approximately 6 cm in diameter, located in the upper segment of the lower lobe of the left lung. The mass was heterogeneous with hypodense areas and amorphous calcifications. No mediastinal lymphadenopathy was observed (Figure 1). 
Pulmonary function tests revealed a mild obstructive ventilatory disturbance. Laboratory data, including rheumatoid factor and antinuclear body, were normal. Bronchoscopy was normal and mycobacterial and fungal cultures of bronchoalveolar lavage fluid were negative. Cytological evaluation was negative for malignant cells. CT-guided percutaneous transthoracic fine needle aspiration cytology of the pulmonary lesion was nondiagnostic. There was no evidence of bacterial or fungal organisms in the collected sample.
An open lung biopsy revealed a mass in the upper segment of the lower lobe of the left lung and fibrous exudate, which was adhered to the pleural surface. The histopathological findings mainly consisted of deposition of hyaline tissue masses accompanied by sparse lymphocytic infiltrate (Figure 2). There was no histological evidence for infectious agents such as TB and fungal organisms. These features were consistent with a diagnosis of pulmonary hyalinizing granuloma. 
The patient received no subsequent specific treatment and he remained asymptomatic. There was no increase in the size of the mass as of the last outpatient followup, which was performed two years after diagnosis.