What is Malignant Myoepithelioma?
Malignant Myoepithelioma, also known as Myoepithelial Carcinoma, is a rare form of cancer primarily affecting the salivary glands, particularly the parotid gland. It may also arise in soft tissues, submandibular glands, or minor salivary glands. This cancer originates from myoepithelial cells, which exhibit characteristics of both muscle and epithelial tissue.
Staging (Cancer Stages)
The AJCC TNM system is used to stage Malignant Myoepithelioma:
- T1: tumour ≤2 cm, confined to the gland.
- T2: tumour 2–4 cm, still confined to the gland.
- T3: tumour >4 cm or extending beyond the gland.
- T4a: tumour invades facial nerve, ear canal, skin, or jawbone.
- T4b: tumour invades major blood vessels or the base of the skull.
Location of the tumour
- Parotid Glands: The most common site, accounting for 48–75% of cases.
- Other Sites: Submandibular glands, minor salivary glands (e.g., palate, tongue, nasal cavity), soft tissue, or bones.
Epidemiology
- Malignant Myoepithelioma is extremely rare, representing only 0.2% of all salivary gland cancers.
- It is more commonly diagnosed in adults but can also occur in children.
Causes
Linked to cellular changes and mutations in salivary gland genes.
Signs and Symptoms
Symptoms depend on the tumour’s location but may include:
General Symptoms
A painless mass or lump that grows rapidly.
Site-Specific Symptoms
1. Nasal Malignant Myoepithelioma
- Abnormal tissue growth in the nose.
- Nasal discomfort or irritation.
- Nosebleeds.
- Nasal obstruction or congestion.
2. Laryngeal Malignant Myoepithelioma
- Hoarseness or changes in voice.
3. Parotid Gland Malignant Myoepithelioma
- Weakness or paralysis of facial muscles.
Diagnosis
A comprehensive diagnostic approach includes:
1. Imaging:
CT scans or MRIs to evaluate tumour size and spread.
2. Biopsy:
Tissue sample analysis under a microscope.
3. Immunohistochemical Markers:
Detection of SMA, S-100 protein, and cytokeratins to confirm the diagnosis.
Treatment
Treatment typically involves a multidisciplinary approach:
1. Surgery:
Primary treatment to completely remove the tumour with clear margins, reducing the risk of recurrence.
2. Radiation Therapy:
Often used after surgery to eliminate residual microscopic disease or when surgery is not feasible.
3. Chemotherapy:
Applied in high-grade, advanced, or recurrent cases, often combined with surgery and/or radiation.
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