What is Mucoepidermoid Lung Tumor?
Mucoepidermoid carcinomas are uncommon tumors found typically in the salivary glands, made up of cells that secrete mucus, flat cells called squamous cells, and other intermediate-type cells. Interestingly, they also represent a unique family of lung cancers, but are quite rare, making up for less than 1% of all lung cancers.
According to the current classification by the World Health Organization, these kinds of lung tumors are further divided into low-grade and high-grade forms. These usually occur in the main airway passages (bronchi). Most of these are low-grade mucoepidermoid carcinomas, which have a pretty good outlook compared to high-grade tumors. The latter behave similarly to other more severe lung cancers.
Diagnosing lung mucoepidermoid carcinoma often depends on examining a sample tissue (biopsy) taken from the patient during surgery, as the symptoms and imaging test results are not particularly specific for this type of cancer.
What Causes Mucoepidermoid Lung Tumor?
Smoking tobacco doesn’t appear to increase the risk of developing a type of lung cancer known as mucoepidermoid carcinoma.
Risk Factors and Frequency for Mucoepidermoid Lung Tumor
Mucoepidermoid carcinomas, a kind of lung tumor, are not very common. They make up only 0.1 to 0.2% of all primary lung tumors. These types of tumors can occur in people of all ages, but about half of the cases are found in people under 30 and 20% are diagnosed in individuals under 20. Both men and women are equally affected. These tumors are usually located within the main parts of the lungs, like the trachea and bronchi, but can sometimes be found in the outer parts of the lungs.
- Mucoepidermoid carcinomas account for 0.1 to 0.2% of all primary lung tumors.
- They can affect people of all ages, with about half of the cases found in individuals below 30 and 20% in those below 20.
- Both males and females are equally likely to be affected.
- These tumors are usually found within main parts of the lungs such as the trachea, main or lobar bronchi, or segmental bronchi.
- Occasionally, they are found on the outer edges of the lungs.
Signs and Symptoms of Mucoepidermoid Lung Tumor
Pulmonary mucoepidermoid carcinoma is a type of lung cancer that is often difficult to diagnose quickly due to its slow growth and vague symptoms. This means it can often take over a year to identify. Additionally, the changes seen on lung scans are often not drastic.
The disease usually shows itself through symptoms that suggest irritation or blockage in the lungs’ large airways. The most common of these symptoms include:
- Spitting blood (Hemoptysis)
- Coughing
- Chest pain
- Wheezing
- Obstructive pneumonia i.e., having a shortened breath because of an obstruction in the lungs
Testing for Mucoepidermoid Lung Tumor
Chest X-rays:
On a chest X-ray, a condition known as mucoepidermoid carcinoma often looks like oval or round shapes that are well-defined and might have different sizes. Sometimes, the X-ray might show signs of blocked airways, such as impacted mucus, an infection caused by obstruction, expansion of the bronchial tubes (the tubes leading to the lungs), collapse of part or all of a lung, trapped air, and unusual lightness in the lung’s periphery.
CT Scans:
When it comes to diagnosing pulmonary mucoepidermoid carcinomas, which is a type of lung cancer, CT scans don’t always give clear results as the findings are non-specific.
On a CT scan, less serious (low-grade) tumors may look like uniform nodules or masses inside the airways with or without signs of obstruction. Some larger, irregular masses may contain multi-lobular cystic structures filled with fluid that looks lighter on the scan, and in some cases, multiple tiny or rough calcifications (abnormal deposits of calcium) are noted.
For more serious (high-grade) tumors, there’s less mucus because the cells are not well differentiated, meaning they don’t have the usual structure and function of mature cells. Cystic lesions (abnormal sacs filled with fluid) are less common in these cases, and the tissue death (necrosis) happens more often. Some high-grade tumors show signs of common lung cancer on CT scans, such as spiculated masses (which have spikes or points), involvement of the pleura (layers of tissue that cover the lungs), swollen lymph nodes, or even spread of the cancer to distant body parts.
PET Imaging:
Positron emission tomography (PET) imaging is another medical imaging technique. Usually, pulmonary mucoepidermoid carcinoma appears very active in a PET scan. The sizes of these carcinomas can range from 0.6 to 6 cm.
Bronchoscopy:
Bronchoscopy is a procedure where the doctor looks into your lungs and air passages. In this procedure, pulmonary mucoepidermoid carcinomas often look like pink, polypoid (polyp-like) masses that can be confused with a different type of tumor, specifically, a carcinoid tumor.
Histopathology:
The definitive diagnosis of pulmonary mucoepidermoid carcinoma depends on examining a sample of the tumor under a microscope (a process called histopathological examination) of tissues obtained from a biopsy or surgery. This is because the signs and symptoms seen in clinics and on imaging studies aren’t specific enough.
Treatment Options for Mucoepidermoid Lung Tumor
The best treatment for pulmonary mucoepidermoid carcinoma, a type of lung cancer, is complete surgical removal of the tumor. This can often result in improved long-term survival. If the disease has progressed or the cancer is high-grade, which means it is more aggressive, and the tumor cannot be entirely removed through surgery, then additional treatments may be needed.
However, the effectiveness of these additional treatments, like chemotherapy and radiotherapy, is still under debate. Some patients with tumors that cannot be surgically removed have experienced positive results from therapies that target a protein called EGFR. But these results still need to be confirmed through more in-depth research.
What else can Mucoepidermoid Lung Tumor be?
When a doctor is trying to diagnose a low-grade mucoepidermoid carcinoma (a type of cancer), they might consider whether it could actually be one of the following conditions instead:
- Mucous gland adenoma
- Carcinoid
- Squamous cell carcinoma
- Adenocarcinoma
Similarly, when diagnosing a high-grade mucoepidermoid carcinoma, they might also consider other possible conditions, such as:
- Adenosquamous carcinoma
- Necrotizing sialometaplasia
- Squamous cell carcinoma
- Adenocarcinoma
What to expect with Mucoepidermoid Lung Tumor
Low-grade mucoepidermoid carcinoma:
Even though there may occasionally be instances where this cancer spreads to nearby lymph nodes or other parts, people with low-grade mucoepidermoid carcinoma have a fantastic prognosis. The five-year survival rate is close to 95%.[13] Additionally, the outlook is slightly better for children as compared to adults.[19]
High-grade mucoepidermoid carcinoma:
The outlook for high-grade cancers differs, but around 25% of people with these tumors undergo metastasis, where the cancer spreads typically to lymph nodes, bones or skin.[12]
There are certain factors that could negatively affect the prognosis:
* When surgeons are unable to completely remove the tumor during surgery (Positive resection margins)
* When the cancer spreads to the lymph nodes.
