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Mucoepidermoid Carcinoma
Mucoepidermoid carcinoma is a malignant glandular epithelial neoplasm characterized by mucous, intermediate and epidermoid cells, with columnar, clear cell and oncocytoid features
Mucoepidermoid carcinoma (MEC) is the most common primary salivary gland malignancy in both adults and children
It is the common malignant neoplasm observed in both major and minor salivary glands
| Low-grade: slow growing, painless mass |
| High-grade: rapidly enlarging, +/- pain |
CLINICAL FEATURES:
- Significant female predilection (3:2 )
- Parotid 45-70% of cases
- Peak incidence in 3rd and 5th decade of life
- Most common in children previously exposed to radiation
- Slowly enlarging, painless mass
- Facial nerve palsy (high grade)
- Trismus, drainage for ear and dysphagia.
- Numbness of adjacent areas.
- Sometimes, ulceration is seen
- Seldom exceeds 5 cm
- Not completely encapsulated
- Often contains cysts,
- Maybe filled with a viscoid, mucoid material
SITE:
- Extraorally: 50% MEC occur in the parotid gland (arising in superficial lobe)
- Intraorally : 20% occur on the palate
- Rest of the lesions arising from the minor salivary glands with the buccal mucosa, lips, tongue and retro molar areas to be the favored sites.
GROSS PATHOLOGY
- Well-circumscribed to partially encapsulated to unencapsulated
- Solid tumor with cystic spaces
HISTOLOGICAL FEATURES
- In almost all cases more solid areas containing cytologically bland, socalled “intermediate cells” are also seen.
- Cysts of variable sizes are often present, and they usually contain brownish fluid.
- MEC cells form sheets, islands, duct-like structures, and cysts of various sizes.
- The cysts may be lined with intermediate, mucous, or epidermoid cells, and they are filled with mucus
- Papillary processes may extend into the cyst lumina, and this is occasionally a conspicuous feature.
- The tumor is primarily made up of three cell types in widely varying proportions: intermediate, mucous, and epidermoid.
| INTERMEDIATE CELLS | MUCOUS CELLS | EPIDERMOID CELLS |
| The intermediate cells frequentl y predominate; their appearance ranges from small basal cells with scanty basophilic cytoplasm to larger and more oval cells with more abundant pale eosinophilic cytoplasm that appears to merge into epidermoid or mucous cells. | Mucous cells (mucocytes) can occur singly or in clusters, and they have pale and sometimes foamy cytoplasm, a distinct cell boundary, and small, peripherally placed , compressed nuclei . Mucocytes often form the lining of cysts or duct-like structures | Epidermoid cells may be uncommon and focally distributed. They have abundant eosinophilic cytoplasm, but they rarely show keratin pearl formation or dyskeratosis. Oncocytic metaplasia is seen occasionally |
TREATMENT
- Influenced by site, stage, grade
- Surgical excision with or without neck dissection.
- Radiotherapy is generally palliative in advanced tumors; it has little impact on prognosis
PROGNOSIS
- The prognosis is dependent on the clinical stage, site, grading, and adequacy of surgery.
- Survival is greater than 95% for low-grade tumors,and regional metastasesare rare.
- The death rate increases to 45% for high-grade tumors.
- Death is usually caused by uncontrolled locoregional disease and metastases to the lung, bone, and brain.
