Pulmonary sarcoma

Primary malignant sarcomas

Primary sarcomas develop directly in the tissues of the respiratory system. In clinical practice, fibrosarcoma (fibrosarcoma) and leiomyosarcoma (leiomyosarcoma) are the most common. Chondrosarcoma, fibroleiomyosarcoma, rhabdomyosarcoma, carcinosarcoma, liposarcoma, osteosarcoma, and pleomorphic undifferentiated sarcoma are diagnosed significantly less often.

Special attention should be paid to angiosarcomas (angiosarcomas) of the pulmonary artery: their distinctive feature is that they arise and spread predominantly intravascularly.

Radiological presentation: Most commonly, primary sarcomas present as a solitary pulmonary nodule or a mass growing in the lumen of the trachea or the endobronchial tree. It is important to understand that standard radiography methods make these tumors visually completely indistinguishable from bronchial carcinoma.

Kaposi sarcoma

The epidemiological surge of this disease was directly linked to the AIDS pandemic, but today the situation has significantly improved thanks to the widespread use of antiretroviral therapy. Isolated involvement of the respiratory tract is extremely rare; as a rule, the pulmonary form is accompanied by skin lesions. The tumor often invades the tracheobronchial tree, although pulmonary parenchyma involvement without overt endobronchial disease is also possible.

Imaging features:

• Focal changes: lobar opacities are most often caused by the tumor mass itself. However, if Kaposi sarcoma grows endobronchially, it can provoke atelectasis or the development of post-obstructive pneumonia.
• Widespread involvement: this is the most typical pattern. It manifests as a perihilar accumulation of linear, rounded, or reticulonodular shadows. Such a pattern reflects the bronchocentric distribution of the pathological process.
• Plain chest radiography often reveals thickening of the interlobular septa, with opacities being most pronounced in the lower lung zones and at the lung roots.
• Computed tomography (CT) clearly demonstrates the peribronchial distribution of ill-defined nodular structures.

Associated manifestations: Intrathoracic lymphadenopathy (enlargement of mediastinal and hilar lymph nodes) is detected in 25–60% of patients. Pleural involvement with effusion formation is also extremely characteristic, which is often bilateral and massive.

Hamartoma: the most common benign tumor

Benign pulmonary neoplasms are uncommon, run a predominantly asymptomatic course, and require quality imaging to determine the need for surgical intervention. A prominent representative of this group is hamartoma (hamartoma).

A hamartoma is a tumor-like malformation. It consists of a chaotic mixture of fully mature tissues normally present in the lungs. Cartilage tissue and clefts lined with bronchial epithelium predominate in its structure, and large islands of adipose tissue may also be present. The risk of malignant transformation of a hamartoma approaches zero. Peak incidence occurs in the seventh decade of life; in children, the tumor is described only in casuistic case reports.

Radiological presentation of hamartoma:

1. Radiography: a spherical or lobulated nodule (usually up to 4 cm in diameter) with clear margins against the background of unchanged lung parenchyma. About 90% of hamartomas grow peripherally, and only 10% centrally, causing large bronchus obstruction (mimicking bronchial carcinoid).
2. Calcification: as the tumor grows, calcium is frequently deposited within it. A specific «popcorn» pattern (popcorn calcification) is formed as a result of cartilage ossification/calcification. This sign is virtually pathognomonic for hamartoma.
3. CT diagnostics: identification of fat density (fat density) areas in the central part of the lesion is a key sign that reliably confirms the diagnosis.

The tumor grows extremely slowly and never undergoes cavitation (formation of disintegrating cavities).

Other rare pulmonary neoplasms

In addition to sarcomas, other extremely rare malignant processes can occur in the lungs. These include pulmonary blastoma, hemangiopericytoma, choriocarcinoma, plasmacytoma, teratoma, and Askin tumors (Askin tumours).

The list of rare benign pulmonary neoplasms is also quite extensive. This group includes lipoma, fibroma, chondroma, hemangioma, benign clear cell tumors, neurogenic neoplasms, chemodectomas (chemodectoma), and granular cell myoblastomas. As with hamartoma, imaging methods play a decisive role in their initial differentiation from aggressive cancerous processes.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Differential diagnosis of central hamartoma and bronchial carcinoid
• Features of intravascular spread of pulmonary artery angiosarcoma
• Rare malignant tumors: pulmonary blastoma and Askin tumors
• The role of antiretroviral therapy in the regression of pulmonary Kaposi sarcoma
• Benign clear cell tumors and pulmonary chemodectomas

Other topics in the «Chest Radiology» section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.