Pulmonary hamartoma is a congenital benign neoplasm of the lungs that develops from various elements of embryonic tissue with a predominance of cartilage, fat, muscle or fibrous components. The clinical picture of a lung hamartoma varies from a complete absence of symptoms to pronounced manifestations, including difficulty breathing, chest pain, cough, sometimes hemoptysis and the development of obstructive pneumonia. The diagnosis is based on radiography, CT and MRI of the chest, transthoracic puncture biopsy. Treatment consists in surgical removal of the tumor.
ICD 10
D14.3 Bronchus and lung
Meaning
Pulmonary hamartoma (hamartochondroma, chondroadenoma, lipohondroadenoma) is a dysembriogenetic lung tumor in which tissue components of the pulmonary parenchyma, distal bronchi and other structures are combined. Hamartoma is one of the most common benign lung formations and the most common form of a peripheral pulmonary tumor (60-64% of cases).
The hamartoma is usually located in the anterior segment of the lower lobes (more often the right lung), in the thickness of the parenchyma (intrapulmonary) or superficially (subpleural). In isolated cases, it can be localized on the inner wall of a large bronchus (endobronchially), protruding into its lumen. Lung hamartoma is characterized by: slow growth over many years, absence of infiltration of lung tissue and metastasis, extremely low risk of malignant transformation. Pulmonary hamartoma is 2-4 times more often detected in males, usually at the age of 30-50 years.
Causes
To date, the question remains the subject of discussion in pulmonology: is a hamartoma a de novo tumor or a consequence of dysembriogenesis and subsequent tumor transformation. Most scientists tend to consider hamartoma a malformation of the lungs, resulting from a violation of the laying and formation of bronchopulmonary structures in embryogenesis. Connective tissue, cartilaginous and smooth muscle components of the pulmonary hamartoma develop from the germ tissue (mesenchyma). Epithelial structures can be involved a second time from the surrounding lung tissue during tumor growth or from the mesodermal and endodermal rudiments of the bronchus.
Risk factors for the occurrence of lung hamartoma may be genetic predisposition, gene disorders, prolonged exposure to mutagens (dangerous chemicals, ionizing radiation) on the body of future parents.
Pathanatomy
Most hamartomas have the appearance of a rounded encapsulated node of dense or elastic consistency with a smooth or finely rounded surface, clearly delimited from the lung parenchyma. The diameter of the tumor can vary from 0.5 mm to 10-12 cm, on average it is 2-3 cm. The composition of the lung hamartoma may include randomly located islands of cartilage tissue, layers of fat, connective tissue and smooth muscle fibers, vascular elements, clusters of lymphoid cells, cavities lined with glandular epithelium and bone inclusions.
Classification
In clinical practice, a local form of hamartoma is predominantly found, rarely diffuse with damage to the entire pulmonary lobe. Hamartomas of the lung are more often single formations, multiple tumors are less common.
The most frequently histologically verified are chonromatous hamartomas of the lung (hamartochondromes) containing a large amount of hyaline cartilage of varying degrees of maturity. A grainy or smooth translucent surface of a grayish-white or whitish-yellow hue is visible on the slice of the node. It is often possible to lick and petrify areas of cartilage tissue.
The structure of leiomyomatous pulmonary hamartoma is dominated by smooth muscle tissue and bronchoalveolar structures. According to its morphological and clinical features, it is similar to hamartochondroma. There are also hamartomas of the lung, containing in excess components of other tissues: fatty (hamartolipoma, lipogamartochondroma), fibrous (hamartofibroma, fibrogamartochondroma), etc. Massive lung hamartomas formed by cells of non-corneating squamous epithelium surrounded by blood vessels and fibers of smooth muscle tissue are described.
According to the severity of the clinical picture, there are 3 degrees of lung hamartoma:
- I – characterized by an asymptomatic course
- II – having scant manifestations
- III – with pronounced symptoms due to tumor growth and compression of surrounding tissues
Symptoms
The symptoms of a pulmonary hamartoma are determined by the size of the tumor, its location relative to the large bronchi, diaphragm and chest wall. Most lung hamartomas are long-term and asymptomatic, the tumor is detected accidentally during chest X-ray or autopsy. The peripheral localization and the small size of the hamartoma cause the absence of clinical manifestations.
When the hamartoma reaches a large size, it begins to squeeze the lung tissue, bronchi, diaphragm and chest wall. The patient begins to worry about shortness of breath, pain in the chest on the side of the lesion, usually occurring at the height of a deep breath and accompanied by coughing, and with serious physical exertion – hemoptysis. Hamartoma compression of a large bronchus gives a clinical picture of a central lung tumor.
With endobronchial localization of hamartoma, a local violation of bronchial patency develops, leading to hypoventilation and segmental (less often lobular) atelectasis of the corresponding lung and obstructive pneumonia. In this case, the course of hamartoma is accompanied by clinical manifestations of a chronic infectious process of the lung.
Multiple pulmonary hamartoma can be a manifestation of the Karney triad, combined with gastric leiomyoblastoma and extraadrenal paraganglioma, or Cowden syndrome, characterized by multiple benign formations of internal organs and a high potential for the development of cancer of the mammary and thyroid glands, gastrointestinal tract, genitourinary organs.
Diagnostics
The diagnosis of pulmonary hamartoma is established according to radiography, CT or MRI of the lungs and transthoracic puncture biopsy with histological examination of the biopsy.
- X-ray diagnostics. On the X-ray and tomogram, the pulmonary hamartoma is usually visualized as a single small (rarely > 2-4 cm) rounded shadow of peripheral localization with sharp and clear contours against the background of unchanged lung tissue. The surface of the tumor may be smooth or bumpy. The intensity of the shadow of the pulmonary hamartoma depends on the size of the node and the content of calcareous inclusions.
There are several radiological variants of the lung hamartoma – shadows of medium intensity and homogeneous structure; heterogeneous shadows of medium intensity with calcification; heterogeneous shadows of medium intensity with layered calcification /compaction in the center and heterogeneous shadows of high intensity with massive inlay. With large sizes of the pulmonary hamartoma (4-5 cm), an increase in the pulmonary pattern may appear due to the convergence of vascular and bronchial branches.
- Endoscopic diagnostics. Bronchoscopy is advisable only with an endobronchial arrangement of the hamartoma.
- Biopsy with histology. To confirm the benign nature of the lung hamartoma, a histological examination of the tumor material taken by transthoracic puncture biopsy, diagnostic thoracoscopy or thoracotomy is performed. In the punctate of the hamartochondroma of the lung, elements of immature cartilage tissue, more mature chondrocytes, cluster-like complexes of cells of cubic or prismatic epithelium, small areas of connective tissue, clusters of lymphoid cells, histiocytes and fat droplets can be detected.
Dynamic observation of the lung hamartoma shows the absence or extremely low rate of tumor growth over a long period. Hamartoma must be differentiated from malignant pulmonary neoplasms (lung cancer, carcinoid, chondrosarcoma), solitary metastases of cancer of other localization (mammary glands and ovaries in women, prostate gland in men, kidneys, etc.), tuberculoma, true benign tumors and lung cysts, echinococcosis. With a pulmonary hamartoma, consultations of a pulmonologist, a phthisiologist, an oncologist, a thoracic surgeon are indicated.
Treatment
With a small (less than 2.5 cm), histologically confirmed lung hamartoma and the absence of compression of surrounding tissues, the patient may be under the dynamic supervision of a pulmonologist for several months. The question of further treatment tactics is decided depending on the presence or absence of an increase in the size of the shadow on the radiograph.
Treatment of pulmonary hamartoma is only operative, it consists in removing the tumor through thoracoscopic or thoracotomic access. In case of peripheral localization of the hamartoma, tumor exfoliation (enucleation) is used, if necessary, segmental and marginal resection of the lung. Removal of the pulmonary lobe (lobectomy) is performed in case of prolonged compression of blood vessels, bronchi, lung parenchyma and complicated course of hamartoma.
The endobronchial hamartoma is removed by bronchotomy with excision of the node, as well as resection of the bronchus together with pathological formation and subsequent suturing or plastic surgery of the defect. To exclude peripheral or endobronchial lung cancer, an urgent intraoperative histological examination of the removed tumor is indicated.
Forecast
With timely surgical treatment of lung hamartoma, the prognosis is favorable, the risk of recurrence is low. With a small amount of thoracic surgery, the ability to work is fully restored. Cases of hamartochondroma malignancy are extremely rare, however, cases of tumor transformation into chondrosarcoma, liposarcoma, fibrosarcoma, adenocarcinoma, epidermoid cancer have been described.
Literature
- Pulmonary Hamartomas: A Single-Center Analysis of 59 Cases. Ulas AB, Aydin Y, Eroglu A. Eurasian J Med. 2022 Oct;54(3):270-273. link
- Symptomatic Pulmonary Hamartoma. Shukla I, Stead TS, Aleksandrovskiy I, Rodriguez V, Ganti L. Cureus. 2021 Sep 23;13(9):e18230. link
- Pulmonary Hamartoma Associated With Lung Cancer (PHALC Study): Results of a Multicenter Study. Fiorelli A, D’Andrilli A, Carlucci A, Vicidomini G, Argento G, Trabalza Marinucci B, Ardissone F, Rapanà R, Sobrero S, Carbognani P, Ventura L, Bocchialini G, Ragusa M, Tassi V, Sollitto F, Loizzi D, Ardò NP, Anile M, Puma F, Rendina EA, Venuta F, Serra N, Santini M. Lung. 2021 Aug;199(4):369-378. link
- Surgical treatment and outcome of pulmonary hamartoma: a retrospective study of 10-year experience. Esme H, Duran FM, Unlu Y. Indian J Thorac Cardiovasc Surg. 2019 Jan;35(1):31-35. link