Pulmonary hamartomas (alternative plural: hamartomata) are benign neoplasms composed of cartilage, connective tissue, muscle, fat, and bone. It is one of the most common benign tumors of the lung and accounts for ~8% of all lung neoplasms and 6% of solitary pulmonary nodules.
Pulmonary chondroma has been used interchangeably with pulmonary hamartoma in the past but they should be considered separate entities due to histological differences 14.
Patients usually present in the 4th and 5th decades of life and they are very uncommon in children. There is a recognized male predilection (M:F = 2.5:1). Most lesions are diagnosed incidentally.
Pulmonary hamartomas are usually asymptomatic and found incidentally when imaging the chest for other reasons. It can occasionally present with hemoptysis, bronchial obstruction, and cough (especially endobronchial types) 6.
Hamartomas may be chondromatous (more common), leiomyomatous, or a mixture. At least two mesenchymal elements are present in them. They are unencapsulated, lobulated tumors with connective tissue septa.
As with any hamartoma it is composed of tissues that normally constitute in the lung and bronchi. The tissue elements, although mature, are disorganized. On rare occasion, they contain principally fatty tissue, in which case they are called lipomatous hamartomas or endobronchial lipomas.
The vast majority of pulmonary hamartomas are located peripherally within the lungs (>90%), with endobronchial hamartomas representing only ~5% (range 1.4-10%) of such lesions 10-11.
Typically, hamartomas manifest incidentally as solitary nodules in the periphery of the lung.
Often discovered incidentally, they are typically well-circumscribed nodules or masses (usually small) with either smooth or lobulated margins. Approximately 60% have fat 7 and approximately 20-30% have calcification/ossification (popcorn-like) 3. Cavitation is not seen.
Size is variable: they can be large (>10 cm) but in most cases, they are <2.5-4 cm in diameter 10,13.
Growth occurs but is very slow, with a typical volume doubling time of over 400 days 9.
Chest radiography is non-specific, demonstrating a soft tissue attenuation, well-circumscribed mass with either smooth or lobulated margins. Calcification (classically popcorn type) may be seen, which can suggest the diagnosis. Fat is difficult to identify with certainty, although the lesion is typically of low density for its size.
CT is far superior in detecting intralesional fat and calcification. The reported prevalence of calcification in hamartomas on CT varies from 5 to 50% while fat may be identified in up to 60% of hamartomas at CT. The fat components may be localized or generalized within the nodule.
Fat can be recognized by comparing it to subcutaneous fat, and will typically have a Hounsfield measurement of -40 to -120 HU 10. Presence of fat in a well-circumscribed solitary pulmonary nodule which does not demonstrate significant growth is essentially pathognomonic of a pulmonary hamartoma and no further investigations are required 7. Unfortunately, fat can only be identified in 60% of lesions. Thin section CT is therefore essential to avoid missing small foci of fat.
Calcification is typically dispersed in the form of multiple clumps throughout the lesion in a popcorn configuration 3.
T1: heterogeneous signal
- mainly intermediate signal 8
- foci of high signal represent fat
- low signal regions representing fibrous or calcific material
- high signal due to fat and cartilaginous components
- low signal regions representing fibrous or calcific material
- T1 C+ (Gd): heterogeneous enhancement is seen
Although uncommon, increased avidity may be seen on FDG-PET 7. Thus, further investigation with PET-CT of slow-growing, fat-containing masses is unwarranted, confusing, and contributes to patient radiation dose.
Treatment and prognosis
Malignant transformation is exceedingly rare, and a peripheral small hamartoma with no atypical features can be safely left alone, with infrequent follow-up to exclude growth.
In atypical cases, or in cases of endobronchial hamartomas causing distal complications, surgical resection is curative. Rigid transbronchial resection is most frequently employed in the later 12.
The differential is somewhat dependent on whether fat or calcification is identifiable within the lesion.
If fat is visualized then the differential is narrow, with almost all cases representing pulmonary hamartoma. See differential of fat containing solitary pulmonary nodule.
Presence of calcification also significantly narrows the differential, but to a lesser degree. See differential of a solitary pulmonary nodule with calcification.
If neither fat nor calcification is present, then the differential is that of a solitary pulmonary nodule and is significantly broader. See differential of a solitary pulmonary nodule.
- 1. Weissleder R, Wittenberg J, Harisinghani MG. Primer of diagnostic imaging. Mosby Inc. (2007) ISBN:0323040683. Read it at Google Books - Find it at Amazon
- 2. Brant WE, Helms CA. Fundamentals of diagnostic radiology. Lippincott Williams & Wilkins. (2007) ISBN:0781765188. Read it at Google Books - Find it at Amazon
- 3. Chai JL, Patz EF. CT of the lung: patterns of calcification and other high-attenuation abnormalities. AJR Am J Roentgenol. 1994;162 (5): 1063-6. AJR Am J Roentgenol (abstract) - Pubmed citation
- 4. Marchiori E, Souza AS, Franquet T et-al. Diffuse high-attenuation pulmonary abnormalities: a pattern-oriented diagnostic approach on high-resolution CT. AJR Am J Roentgenol. 2005;184 (1): 273-82. AJR Am J Roentgenol (full text) - Pubmed citation
- 5. Gaerte SC, Meyer CA, Winer-muram HT et-al. Fat-containing lesions of the chest. Radiographics. 2002;22 Spec No : S61-78. Radiographics (link) - Pubmed citation
- 6. Thomas JW, Staerkel GA, Whitman GJ. Pulmonary hamartoma. AJR Am J Roentgenol. 1999;172 (6): 1643. AJR Am J Roentgenol (citation) - Pubmed citation
- 7. Klein JS, Braff S. Imaging evaluation of the solitary pulmonary nodule. Clin. Chest Med. 2008;29 (1): 15-38, v. doi:10.1016/j.ccm.2007.11.007 - Pubmed citation
- 8. Kauczor H, Baert AL. MRI of the Lung. Springer Verlag. (2009) ISBN:354034618X. Read it at Google Books - Find it at Amazon
- 9. Naidich DP, Srichai MB, Krinsky GA. Computed tomography and magnetic resonance of the thorax. Lippincott Williams & Wilkins. (2007) ISBN:0781757657. Read it at Google Books - Find it at Amazon
- 10. Collins J, Stern EJ. Chest radiology, the essentials. Lippincott Williams & Wilkins. (2007) ISBN:0781763142. Read it at Google Books - Find it at Amazon
- 11. Cosío BG, Villena V, Echave-sustaeta J et-al. Endobronchial hamartoma. Chest. 2002;122 (1): 202-5. doi:10.1378/chest.122.1.202 - Pubmed citation
- 12. Ishibashi H, Akamatsu H, Kikuchi M et-al. Resection of endobronchial hamartoma by bronchoplasty and transbronchial endoscopic surgery. Ann. Thorac. Surg. 2003;75 (4): 1300-2. - Pubmed citation
- 13. Siegelman SS, Khouri NF, Scott WW et-al. Pulmonary hamartoma: CT findings. Radiology. 1986;160 (2): 313-7. Pubmed citation
- 14. Rodriguez FJ, Aubry MC, Tazelaar HD et-al. Pulmonary chondroma: a tumor associated with Carney triad and different from pulmonary hamartoma. Am. J. Surg. Pathol. 2007;31 (12): 1844-53. doi:10.1097/PAS.0b013e3180caa0b5 - Pubmed citation
Related Radiopaedia articles
- imaging techniques
- frontal projection
- lateral projection
- lateral decubitus
- congenital heart disease
- medical devices in the thorax
- common lines and tubes
- nasogastric tubes
- endotracheal tubes
- central venous catheters
- pleural catheters
- cardiac conduction devices
- prosthetic heart valve
- review areas
- differential diagnoses of airspace opacification
- lobar consolidation
- lobar lung collapse
- chest x-ray in the exam setting
- cardiomediastinal contour
- chest radiograph zones
- tracheal air column
- normal chest x-ray appearance of the diaphragm
- nipple shadow
lines and stripes
- anterior junction line
- posterior junction line
- right paratracheal stripe
- left paratracheal stripe
- posterior tracheal stripe/tracheo-esophageal stripe
- posterior wall of bronchus intermedius
- right paraspinal line
- left paraspinal line
- aortic-pulmonary stripe
- aortopulmonary window
- azygo-esophageal recess
- air bronchogram
- big rib sign
- Chang sign
- Chen sign
- coin lesion
- continuous diaphragm sign
- dense hilum sign
- double contour sign
- egg-on-a-string sign
- extrapleural sign
- finger in glove sign
- flat waist sign
- Fleischner sign
- ginkgo leaf sign
- Golden S sign
- Hampton hump
- haystack sign
- hilum convergence sign
- hilum overlay sign
- Hoffman-Rigler sign
- holly leaf sign
- incomplete border sign
- juxtaphrenic peak sign
- Kirklin sign
- medial stripe sign
- melting ice cube sign
- more black sign
- Naclerio V sign
- Palla sign
- pericardial fat tag sign
- Shmoo sign
- silhouette sign
- snowman sign
- spinnaker sign
- steeple sign
- straight left heart border sign
- third mogul sign
- tram-track sign
- walking man sign
- water bottle sign
- wave sign
- Westermark sign
- chest x-ray
- small airways disease
- broncho-arterial ratio
- related conditions
- differentials by distribution
- pulmonary edema
interstitial lung disease (ILD)
- drug-induced interstitial lung disease
- acute hypersensitivity pneumonitis
- subacute hypersensitivity pneumonitis
- chronic hypersensitivity pneumonitis
- bird fancier's lung: pigeon fancier's lung
- farmer's lung
- cheese workers' lung
- mushroom worker’s lung
- malt worker’s lung
- maple bark disease
- hot tub lung
- wine maker’s lung
- woodsman’s disease
- thatched roof lung
- tobacco grower’s lung
- potato riddler’s lung
- summer-type pneumonitis
- dry rot lung
- machine operator’s lung
- humidifier lung
- shower curtain disease
- furrier’s lung
- miller’s lung
- saxophone lung
idiopathic interstitial pneumonia (mnemonic)
- acute interstitial pneumonia (AIP)
- cryptogenic organizing pneumonia (COP)
- desquamative interstitial pneumonia (DIP)
- non-specific interstitial pneumonia (NSIP)
- idiopathic pleuroparenchymal fibroelastosis
- lymphoid interstitial pneumonia (LIP)
- respiratory bronchiolitis–associated interstitial lung disease (RB-ILD)
- usual interstitial pneumonia / idiopathic pulmonary fibrosis (UIP/IPF)
non-small-cell lung cancer
- pre-invasive tumors
- minimally invasive tumors
- invasive tumors
- variants of invasive carcinoma
- described imaging features
- adenosquamous carcinoma
- large cell carcinoma
- primary sarcomatoid carcinoma of the lung
- squamous cell carcinoma
- salivary gland-type tumors
- pulmonary neuroendocrine tumors
- preinvasive lesions
- lung cancer invasion patterns
- tumors by location
- benign neoplasms
- pulmonary metastases
- lung cancer screening
- lung cancer staging
- non-small-cell lung cancer