대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Hamartoma

Radiologic Findings

Chest radiograph shows a well-demarcated large mass in the right suprahilar area. On pre-enhanced CT, a huge well-demarcated heterogeneous density of mass composed of multiple popcorn-like and stippled calcifications and low attenuated portion in the right upper lobe and tethered to the right minor fissure. On post-enhanced CT, the large mass reveals marginal well enhanced portion and mainly poorly enhanced portion including typical calcifications. On microscopic findings, pulmonary parenchymal hamartoma composed predominantly of irregular and broad cartilage masses. The cartilage is surrounded by a rim of fat or fibromyxoid connective tissue. The peripheries are lined by respiratory epithelium.
Hamartomas are the most common benign lung neoplasms and pathologically composed of cartilage with clefts lined by bronchial epithelium and fat, or cystic collections of fluid. Some authors prefer the term “hamartochondroma” or “chondromatous hamartoma” to distinguish these lesions from the much rarer vascular hamartomas that do not contain cartilage.
Most tumors present as a solitary asymptomatic parenchymal lung nodule that may gradually increase in size. Pulmonary hamartomas typically are well-circumscribed solitary nodules, the majority smaller than 4 cm in diameter, without lobar predilection. Approximately one-third have a smooth outline, which may aid in differentiation from the almost invariably lobulated pulmonary carcinoma. Over 90% are situated peripherally, with 8 % or less arising in central bronchi. The peripheral lesions are asymptomatic; the endobronchial hamartomas may cause of bronchial obstruction and hemoptysis. The average age at presentation of pulmonary hamartoma is 45 to 50 years. They are rarely seen in children. The diagnostic radiograph finding of popcorn pattern of calcification occurs in fewer than 30 percent of patients. Percutaneous transthoracic needle biopsy yields diagnostic information in as many as 85 percent of patients. The patient with peripheral hamartoma may be safely observed, as malignant transformation is rare. The pulmonary hamartoma can be specifically recognized when focal deposits of fat are identified by a CT number in the -80 to -120 HU range. Hamartomas represent a very small proportion of all pulmonary nodules, but because they are frequently not recognized preoperatively, they account for 6-8% of all resected pulmonary nodules. Cartilage is generally the dominant mesenchymal component of the lesion, often leading to calcification. The larger the lesion, the more likely that it will calcify. Definite calcification is seen on plain film in up to 15%. Some researchers reported in 20 resected solitary hamartomas of the lung. Analyzing the lesions histologically, they found fatty tissue in 7 cases and chondroid tissue in 13 of 20. Some reporters concluded that nodules measuring 2.5 cm of less with smooth edges and demonstrating focal collections of fat (or fat alternating with areas of calcification) warranted a firm diagnosis of hamartoma and should be conservatively managed. Hamartomas can be multiple but rare.

Brief Review

References

1. Armstrong P. Neoplasms of the lung. In Armstrong P, Wilson AG, Dee P, Hansell DM. Imaging of disease of the chest. St. Louis, Mosby. 1995: 272-368
2. Yamashita K, Matsunobe S, Tsuda T et al. Solitary pulmonary nodule: preliminary evaluation with incremental dynamic study. Radiology. 1995;194:399-405
3. Naidich DP, Zerhouni EA, Siegelman SS. Computed tomography and magnetic resonance of the thorax. New York. Raven Press. 1991 : 303-338

Keywords

Lung, Benign tumor,