Introduction:
Pulmonary mucoepidermoid carcinoma (PMEC) is a very rare type of cancer, accounting for only 0.1 percent to 0.2 percent of all lung cancers. Despite their rarity, they can occur in individuals of all ages, affecting both men and women equally. Despite their rarity, they can occur in individuals of all ages. However, they tend to be more common in younger people, with about 50 percent of cases occurring before the age of 30 and around 20 percent before the age of 20. PMEC is best managed by a team with multiple specialties that include a pathologist, radiologist, thoracic surgeon, oncologist, and pulmonologist. For the majority of patients, an early diagnosis and timely treatment enhance the prognosis. This article briefly explains Pulmonary Mucoepidermoid Carcinoma, including its cause, symptoms, diagnosis, treatment, and prognosis.
What Is Pulmonary Mucoepidermoid Carcinoma?
PMEC is a very uncommon type of lung cancer, which makes up less than 1 percent of all lung cancers. It originates from the minor salivary glands located in the submucosal lining of the airways within the lungs. These glands typically produce mucus to keep the airways moist and lubricated. However, in PMEC, these cells develop abnormally, forming a tumor.
Based on the aggressiveness and growth rate of the tumors, PMEC can be divided into low-grade and high-grade tumors. Low-grade cancers typically carry a better prognosis and are less concerning.
What Are the Symptoms Of Pulmonary Mucoepidermoid Carcinoma?
PMEC often presents with symptoms similar to other lung conditions, including:
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Hemoptysis–Coughing up blood.
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Cough–This can be persistent or occasional.
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Chest Pain–carcinoma may cause chest pain that worsens while coughing.
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Wheezing–A high-pitched whistling noise while taking a breath, indicating respiratory tract tightening.
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Obstructive Pneumonia–This happens when a tumor obstructs an airway, causing inflammation and infection in the impacted lung area.
How Is Pulmonary Mucoepidermoid Carcinoma Diagnosed?
1. Chest X-Ray: Chest X-rays can be useful. They may not provide an accurate diagnosis for PMEC. Typically, on a chest X-ray, PMEC presents as defined masses within the lungs. These masses may exhibit shapes like oval, round, or lobulated.
2. CT (Computed Tomography) Scan: CT scans provide in-depth details compared to X-rays, though they are not conclusive. In low-grade PMEC cases, solid masses are observed within the airways with borders. On the other hand, high-grade PMEC may have a more solid appearance with fewer fluid-filled areas (cysts) than low-grade cases.
3. Positron Emission Tomography (PET) Scan: This specific scan utilizes tracers to evaluate the activity of tumors. Typically, PMEC exhibits activity on PET scans.
4. Bronchoscopy: This involves inserting a thin tube with a camera into the airways for direct visualization. PMEC may show up as polyp-shaped growths that could look similar to tumors requiring further examination.
5. Biopsy: This is the most important step for the diagnosis of PMEC. A sample of tissue is collected and examined under a microscope (histopathology) to confirm the specific type of cancer cells that help differentiate PMEC from other conditions.
What Is the Treatment of Pulmonary Mucoepidermoid Carcinoma?
The best course of treatment for PMEC is complete surgical removal, particularly for low-grade or early-stage tumors. It increases long-term survival and provides the highest possibility of a cure.
In case of high-grade PMEC, or complete removal is not possible due to some factors, additional treatments might be considered, like adjuvant therapy; this refers to treatment given after surgery to improve outcomes and reduce the risk of recurrence. It includes chemotherapy and radiotherapy, but the use of these adjuvant therapy is still controversial.
EGFR-targeted therapy uses drugs that target specific molecules (EGFR) found in some cancer cells. Some studies show positive responses in some patients. However, more research is needed to confirm these findings and determine their wider applicability.
What Is the Differential Diagnosis of Pulmonary Mucoepidermoid Carcinoma?
Pulmonary mucoepidermoid carcinoma is difficult to diagnose because of the nonspecific symptoms that resemble other lung conditions. Following are some of the conditions that are often diagnosed as PMEC:
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Mucous Gland Adenoma: It is a rare benign tumor of the lungs arising from mucus glands lining the respiratory tract. In histological findings, it often resembles low-grade mucoepidermoid carcinoma.
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Carcinoid: In carcinoid tumors, the neuroendocrine cells of the lungs grow slowly in an abnormal way and give rise to carcinoid tumors. These tumors show similar symptoms like cough, wheezing, and hemoptysis, which are often seen in PMEC.
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Squamous Cell Lung Carcinoma: It is a slow-growing lung cancer that shows symptoms similar to PMEC.
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Adenosquamous Carcinoma: This is a type of lung cancer that has components of both squamous and glandular cells. Although some characteristics are similar to high-grade PMEC.
What Is the Prognosis of Pulmonary Mucoepidermoid Carcinoma?
Low-grade mucoepidermoid carcinoma has a very good prognosis, with a five-year survival rate that is very close to 95 percent. Children have a marginally better prognosis than adults.
The prognosis for high-grade tumors varies, but approximately 25 percent of patients with these tumors experience metastases (spread of cancer), which usually occur in the skin, bone, or lymph nodes.
Conclusion:
Pulmonary Mucoepidermoid Carcinoma, is an uncommon lung cancer that arises from salivary glands lining the airways. The symptoms often mimic other lung conditions, which makes it difficult to diagnose. There has been progress in imaging techniques and histological analysis (biopsy) that help medical professionals distinguish PMEC from other lung conditions. Even though it is a rare type of cancer, low-grade PMEC shows a better prognosis and increased survival rates than high-grade tumors.
