What is Pleuropulmonary Blastoma?
Childhood lung tumors are very rare and only make up between 0.5% to 1% of all the lung tumors that are cancerous. There are three specific types of these tumors: pulmonary blastoma, fetal adenocarcinoma, and pleuropulmonary blastoma (PPB). Fetal adenocarcinoma is characterized typically by cancerous and immature cells. Pleuropulmonary blastoma, on the other hand, is characterized by the abnormal growth of immature tissues. Pulmonary blastoma is identified by having both these traits, resembling a lung within 10 to 16 weeks of pregnancy.
The World Health Organization (WHO), in its 2015 Classification, groups these types: fetal adenocarcinoma under adenocarcinomas, pulmonary blastoma under sarcomatoid carcinoma (a rare type of cancer that begins in the soft tissues or bones), and pleuropulmonary blastoma under mesenchymal tumors (tumors made up of spindle-shaped cells). Pleuropulmonary blastomas, though rare, show no specific symptoms. Despite our reliance on imaging studies like x-rays and CT scans to suspect this condition, a definitive diagnosis is established through microscopic examination of the tumor cells.
The pleuropulmonary tumor goes by many names in medical literature. Some of these are cystic mesenchymal hamartoma, mesenchymal cystic hamartoma, pediatric pulmonary blastoma, pneumoblastoma, pulmonary and lung rhabdomyosarcoma (a rare type of cancer that often starts in the muscles).
What Causes Pleuropulmonary Blastoma?
About 40% of cases are found to be genetically related. These genetic forms are termed as pleuropulmonary blastoma family tumor and dysplasia syndrome, or simply DICER1 syndrome. People diagnosed with this syndrome usually experience abnormal growth and development issues in the early years of life, typically between 5 to 6 years old. However, there are also a few rare cases reported during the teenage years.
The syndrome is linked with faults in the DICER1 gene (so-called loss-of-function mutations) in some families, leading to the loss of DICER1 protein in specific cells, called epithelial cells. It’s worth mentioning that not everyone carrying these DICER1 gene changes will show symptoms.
Reference to a genetic form of the illness can be made, particularly when patients come in with a mixture of symptoms, such as irregular menstrual cycles or other hormone-related symptoms, along with respiratory problems. It’s always important to keep the potential of a genetic cause in mind while diagnosing such cases.
Risk Factors and Frequency for Pleuropulmonary Blastoma
Pleuropulmonary blastomas, a type of lung tumor, are mainly found in young children, typically before the age of 4. These tumors are categorized into three different types based on their characteristics and the typical age that they occur.
- Type I pleuropulmonary tumors: These are purely cystic tumors, typically found in children younger than 2 years, with the average age at diagnosis being 10 months old.
- Type II pleuropulmonary tumors: These tumors are a mix of cystic and solid, and generally occur at an average age of 35 months old.
- Type III pleuropulmonary tumors: These are solid tumors and typically occur at an average age of 41 months old.
Signs and Symptoms of Pleuropulmonary Blastoma
Children affected by different types of tumors associated with the lung or chest will show different signs and symptoms:
- Type I tumors often cause breathing problems due to air-filled cysts pressing on the airways. This can sometimes also cause a lung to collapse (pneumothorax).
- Children with Type II and III tumors might feel shortness of breath and chest pain. They may show signs similar to pneumonia or other general symptoms such as cough, fever, struggle breathing, feeling tired, lack of energy, and loss of appetite.
In some cases, children may not show any symptoms. The condition may be detected due to an unusual shape of the chest wall or an abruptly occurring lung collapse (tension pneumothorax).
Testing for Pleuropulmonary Blastoma
Pleuropulmonary blastomas, a type of lung cancer, usually affect the lung and the pleura, the tissue that lines the inside of the chest cavity. A CT-scan, which is a type of X-ray, can display this as either a lump or an area of the lung that’s denser than normal. It might also show changes that look like multiple little sacs or solid areas. About half to slightly more than half of the most basic type of this cancer is found only in the lungs. However, the cancer spreading beyond the lungs is more typical for more advanced types.
Interestingly, up to a quarter of pleuropulmonary blastoma patients seem to have an inborn and possibly inherited likelihood to develop other types of abnormal or cancerous diseases. These associated conditions could include brain tumors (medulloblastomas), thyroid tumors, cancerous germ cell tumors, and others. Therefore, it’s important for all patients with pleuropulmonary blastomas, and their families, to be thoroughly checked. The reason is to identify any other concerns early and to understand their disease better.
Treatment Options for Pleuropulmonary Blastoma
Patients with type I Pleuropulmonary Blastoma (PPB) – a rare type of lung tumor most commonly found in children – are often treated with surgery to identify and remove the tumor. Some medical experts suggest additional chemotherapy, but there isn’t an established agreement on this point. Radiation therapy, a type of treatment that uses high-energy waves to destroy cancer cells, isn’t typically used for type I PPB. If type I PPB recurs in a child as type II or III (more aggressive versions of the disease), treatments for type II and III would be used.
Type II and III PPB are indeed more aggressive tumors. For patients with these types of lesions, surgeons typically aim to remove the tumor if possible, followed by chemotherapy and/or radiation therapy. Chemotherapy is a method of treating cancer with drugs that kill cancer cells or stop them from growing. Another possible treatment, mentioned in some medical literature, is the use of intracavitary chemotherapy where drugs are directly injected into the cavity where the tumor exists. Treatment plans may include the use of doxorubicin-based regimes, a type of chemotherapy often used in cancer treatment. Recurrence, or the return of cancer, often occurs locally or in the area where the cancer was initially found.
Radiation therapy could be an optional treatment for PPB patients. Specifically, if a minor part of the tumor cannot be surgically removed and it’s resistant to chemotherapy, radiation therapy might be contemplated. Unfortunately, PPB has the potential to spread widely. If it spreads to the brain, surgery followed by radiation therapy is usually suggested. For tumors that return, high-dose consolidation therapy, which is a high dose of chemotherapy, in conjunction with autologous stem cell rescue, a procedure to replace blood-forming stem cells that were destroyed by the chemotherapy, is often recommended.
What else can Pleuropulmonary Blastoma be?
When a doctor is trying to identify the cause of certain symptoms, they look at several possibilities. In the case of certain lung conditions, the major conditions to consider for diagnosis are:
- Synovial sarcoma: This is identified by the presence of specific cell types, known as spindle cells, and certain markers. However, these markers aren’t typically found in pleuropulmonary blastoma, which is a type of lung tumor. Special tests are needed to check for certain genetic changes that could help distinguish these conditions.
- Congenital cystic adenomatoid malformations: These are a type of non-cancerous lung cysts.
- Fetal lung interstitial tumor: This condition shows characteristics similar to the lung at 20 to 24 weeks of pregnancy.
Each of these conditions requires different tests to confirm the diagnosis.
What to expect with Pleuropulmonary Blastoma
Patients with type I tumors have a high likelihood (between 80% to 90%) of being disease-free within five years. However, patients with types II and III tumors have less than a 50% chance of being disease-free during the same period.
