Pulmonary Hamartoma

Etiology, Prevalence, and Epidemiology

Pulmonary hamartomas are benign neoplasms, probably derived from bronchial wall mesenchymal cells. Hamartomas are the most common benign pulmonary neoplasm and account for about 8% of primary lung tumors. Although they may be seen in adolescents and young adults, most cases occur in patients older than 40 years; the peak incidence is in the seventh decade of life. Men are affected two to three times more often than women. Endobronchial hamartomas are much less common than parenchymal lesions, accounting for 5% to 20% of pulmonary hamartomas.

Although hamartomas are benign neoplasms, they may rarely coexist with pulmonary carcinoma. Occasionally, they may be multiple. Multiple pulmonary hamartomas may be part of the Carney triad or, rarely, the Cowden syndrome. The Carney triad consists of pulmonary chondroma (often multiple), gastric epithelioid leiomyosarcoma, and functioning extraadrenal para­ganglioma. This rare disease usually affects women younger than 35 years. It is recommended that patients with multiple pulmonary hamartomas have further examinations to rule out gastric leiomyosarcoma and extraadrenal paragangliomas.

Clinical Presentation

Pulmonary hamartomas usually do not cause symptoms. Occasionally, patients may present with hemoptysis or cough. Endobronchial hamartomas may result in bronchial obstruction, and patients may present with cough, hemoptysis, and recurrent pneumonia.

Pathophysiology

Most hamartomas are solitary, well-circumscribed, slightly lobulated tumors located within the parenchyma, usually in a peripheral location. Most measure 1 to 4 cm in diameter, but tumors 25 cm in diameter have been described. On cut section the tumors consist of lobules of white, cartilaginous-appearing tissue. Histologically, the lobules are often composed of a central area of more or less well-developed cartilage surrounded by loose fibroblastic tissue. Adipose tissue, smooth muscle, and seromucinous bronchial glands also may be seen. Calcification and ossification of the cartilage can be present and are occasionally extensive. Although endobronchial hamartomas can be morphologically identical to the parenchymal variety, more often they appear as fleshy, polypoid tumors attached to the bronchial wall by a narrow stalk. Endobronchial hamartomas typically contain more macroscopic fat than parenchymal hamartomas.

Manifestations of the Disease