Pleuropulmonary blastoma (PPB) is a type of cancer that primarily affects children. It often develops in the tissues of the lung and the pleura, but can develop in the organs located in the mediastinum such as the heart, trachea and oesophagus.
The respiratory system is composed of the nose, mouth, trachea (windpipe) and airways (bronchi and bronchioles) that lead to the lungs, which is where the breathing process primarily occurs. Each lung is made up of lobes, with the right lung being composed of three lobes and the left only having two lobes to accommodate room for the heart. The lungs sit on top of a muscle called the diaphragm, which separates the abdomen from the chest. The diaphragm works by contracting/flattening when we inhale, pulling air into the lungs. When we exhale, the diaphragm relaxes and pushes air out of the lungs. The space between the lungs is called the mediastinum, and holds several important structures, including the heart, trachea, oesophagus and lymph nodes.
Each lung is covered by a thin layer of tissues called pleurae, that protects and cushions the lungs. There are two types of pleurae: the parietal and visceral. The parietal pleura is the thicker tissue that lines the inner surfaces of the thoracic cavity, while the visceral pleura lines the surface of the lungs.
PPB is a paediatric cancer that affects the genders equally, and tends to develop in children under the age of eight (most commonly between the ages of three and four). However, anyone can develop this disease.
Types of Pleuropulmonary Blastoma
There are three primary types of PPB, that are categorised by the characteristics of the tumour itself.
Type I Pleuropulmonary Blastoma
Type I PPB is characterised by the development of cysts (abnormal growths that are usually filled with liquid or air) in the lungs, with no evidence of solid tumour parts. These tumours may have some cancerous cells present, and generally occur in patients under three years old. Type I PPB usually has a good prognosis.
Type Ir Pleuropulmonary Blastoma
Type Ir PPB is a subtype of type I PPB that shares the same characteristics, without the presence of cancerous cells. The ‘r’ after type I stands for regressed, which means the cysts have gotten smaller.
Type II Pleuropulmonary Blastoma
Type II PPB shows evidence of cysts and solid tumour parts with cancerous cells. This type of PPB often develops in children around three years old, and can metastasise (spread) to the brain and/or other parts of the body. Type II PPB may be aggressive, and may not have as good of a prognosis as type I PPB.
Type III Pleuropulmonary Blastoma
Type III PPB is a completely solid cancerous tumour that often develops around four years of age. It is often aggressive, likely to metastasise, and may not have as good of a prognosis as other PPB subtypes.
Treatment
If PPB is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
Due to the rarity of this disease, the staging system for this tumour solely relies on determining the type of PPB you have. The factors taken into consideration when staging your tumour may include:
- Presence of cysts.
- Presence of solid tumour.
- Presence of cancerous cells.
- Rate of metastasis (if any).
Your doctor may also recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. This is often performed after a biopsy and can help guide treatment options for you.
Treatment is dependent on several factors, including age, stage of disease and overall health.
Treatment options for PPB may include:
- Surgery, potentially including:
- Lobectomy (removal of a lobe of a lung).
- Extrapleural pneumonectomy (removal of the diseased lung, part of the pericardium (membrane covering the heart), part of the diaphragm and part of the parietal pleura).
- Chemotherapy.
- Radiation therapy (only in patients with PPB types II and III).
- Watch and wait (only in patients with type Ir PPB).
- Clinical trials.
- Palliative care.
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Risk factors
Due to the rarity of PPB, there have been very few risk factors identified. The factors found to potentially increase your risk of developing this disease include:
- Having a mutation of the DICER1 gene.
- Having a family history of cancer.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Early symptoms
PPB may be asymptomatic in the early stages of the disease. As the tumour develops, some symptoms may occur, including:
- Persistent cough.
- Difficulty breathing.
- Unexplainable shortness of breath.
- Fevers.
- Persistent lung infections, such as pneumonia.
- Unexplainable weight loss and/or loss of appetite.
- Chest pain.
Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have PPB, they will order a range of diagnostic tests to confirm the diagnosis, and refer you to a specialist for treatment.
Physical examination
Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.
Imaging & blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-ray, bone scan and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health.
Exploratory procedures & biopsy
You may require an exploratory procedure if the imaging scans were inconclusive, or if there were any abnormalities detected in your previous tests.
Bronchoscopy
A bronchoscopy is a day procedure that examines the trachea and lungs. A long, thin tube with a light and camera attached (bronchoscope) is inserted through the mouth or nose and into trachea and lungs to check for any abnormalities.
Mediastinoscopy
A mediastinoscopy is a day procedure that examines the mediastinum (area between the lungs). The surgeon will make a small incision in the front of your neck, and insert a long, thin tube with a light and camera attached along the outside of the trachea to check for any abnormalities.
Thoracoscopy
A thoracoscopy is often used if other exploratory procedures have provided inconclusive results. A long, thin tube with a light and camera attached (thoracoscope) is inserted into the chest via a small incision between two of your ribs to check for any abnormalities.
Once the location(s) of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle, and can be done during any of the exploratory procedures mentioned above. The tissue sample will then be analysed for cancer cells.
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, early-stage PPB (types I and Ir) have a better prognosis and survival rates. However, if the cancer is advanced (types II and III) and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.