Mucoepidermoid carcinoma

[Anonymous]

Mucoepidermoid carcinoma is a malignant tumor composed of a variable admixture of epidermoid and mucous cells arising from the ductal epithelium of the salivary glands. This is the most common malignant salivary gland tumor (35%). Just over half occurs in the major salivary glands, most commonly the parotid gland; the rest are found in the minor glands, with the palate being the most frequent location. The aggressiveness of the lesion varies with the histologic grade. A wide age range exists, with the highest prevalence in the fifth decades of life. A slight predilection for female exists. The low grade variety rarely metastasizes. Clinically, this nodule not unlike a benign mixed tumor. It is usually only 1-4 cm in diameter. The prognosis is good. The 5 year survival rate is greater than 95%. In contrast to low grade mucoepidermoid carcinomas, high-grade tumors often cause pain and paralysis, have ill defined margins and are relatively immobile. Metastasis by blood and lymph are common, with recurrence in half the patients after excision. The prognosis is poor and varies with the histologic grade, the 5 –year survival rate may be as low as 25%.

        

[Anonymous]

DIFFERENTIAL DIAGNOSIS
MUCOEPIDERMOID CARCINOMA
Tumor composed of mucous, squamous and intermediate cells

Diagnostic Pearls

* Well circumscribed, cystic with mucin pools (low grade) or infiltrative, solid (high grade)
* Varying mixture of mucous, intermediate and epidermoid cells
* Uniform cells with intracytoplasmic mucin (low grade) or pleomorphic cells with little mucin (high grade)

ADENOID CYSTIC CARCINOMA
Cribriform pattern is common

Diagnostic Pearls

* Invasion of stroma and perineural invasion
* Basaloid cells forming cribriform structures, tubules or solid islands
* Chondromyxoid matrix is absent

WARTHIN S TUMOR
Cysts and glands with lymphoid stroma

Diagnostic Pearls

* Multiple large fluid filled cysts
* Double layered epithelial lining with columnar oncocytes and basal cells
* Heavy lymphoid stroma often with germinal centers

        

[Anonymous]

Special Stains and Immunohistochemistry

* Simple mucin-type carbohydrate antigens (T, Tn, and syalosyl-Tn) detected13
* Low-grade type:
o characteristic profile suggestive of striated duct differentiation:
+ CK7
+ CK14
+ mitochondrial antibodies

Staging/Grading

* Traditional two-tier system
* Three-grade scheme:
o proposed by AFIP authors17–19
o based on a points system:
+ intracystic component >20%, 2 points
+ neural invasion, 2 points
+ necrosis, 3 points
+ 4 or more mitoses per 10 HPF, 3 points
+ anaplasia, 4 points
o total score:
+ 0–4 low grade
+ 5–6 intermediate grade
+ ⩾ 7 high grade20

        

[Author]

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