Pulmonary Hyalinizing Granuloma: Case Report and Discussion of Diagnostic Challenges and Terminology.

Pulmonary hyalinizing granuloma (PHG) is a rare, benign condition characterized by slow-growing pulmonary nodules, often mimicking malignant lesions radiologically. Its pathogenesis is unclear but is thought to result from an exaggerated immune response to persistent antigenic stimuli. This report presents a case of a 71-year-old male with PHG, incidentally detected during imaging for acute appendicitis. Diagnostic challenges arose due to the radiological resemblance to metastatic disease, and inadequate biopsy samples. Surgical resection revealed fibrocollagenous nodules with perivascular inflammatory infiltrates. Immunohistochemistry and special stains excluded malignancy and infection. The clinical course of PHG is typically benign, with surgery being the treatment of choice for solitary lesions. However, the current terminology may be misleading, as the lesions are not true granulomas but rather fibrosing lesions. Further research is needed to clarify the underlying pathophysiology and improve diagnostic accuracy.