Pulmonary Hamartoma

Pulmonary hamartoma is a benign neoplastic proliferation of disorganized normal mesenchymal tissue components of the lung (cartilage, adipose tissue, fibrous tissue, smooth muscle) with entrapped respiratory epithelial elements lining clefts and tubules. It is the most common benign lung tumor, accounting for approximately 75% of all benign lung neoplasms and 8% of solitary pulmonary nodules. Despite the historical 'hamartoma' (developmental malformation) classification, recent evidence including HMGA2 gene rearrangements supports a true neoplastic origin.

Most pulmonary hamartomas (90%) are peripheral parenchymal lesions; 10% are endobronchial, presenting with obstructive symptoms (cough, hemoptysis, recurrent pneumonia, atelectasis). They typically occur in adults aged 40–70 years with a male predominance. Most are asymptomatic and discovered incidentally on chest imaging performed for unrelated reasons.

CT scan is the imaging modality of choice. Typical features allow definitive diagnosis: well-circumscribed solitary nodule, popcorn-pattern (chondroid) calcification in 15–20%, intralesional fat (CT density –40 to –120 HU) in approximately 60% of cases. PET-CT shows low or absent FDG uptake. When imaging is diagnostic, observation with serial CT is sufficient. Atypical features warrant biopsy (CT-guided transthoracic, transbronchial) or surgical resection. Endobronchial hamartomas may be treated with bronchoscopic removal or sleeve resection. Surgical wedge resection or enucleation cures peripheral hamartomas with rare recurrence.