Mucoepidermoid Carcinoma

§ overviewOverview

Malignant epithelial salivary gland neoplasm characterised by variable proportions of mucous, intermediate and squamoid cells.

§ icdICD Classification

C07/C08

§ etiologyEtiology

• 01Sporadic; ionising radiation increases risk
• 02CRTC1(MECT1)-MAML2 fusion in ≈50–70%

§ epidemiologyEpidemiology

≈30% of salivary malignancies; parotid > minor glands (palate); commonest salivary malignancy in children.

§ clinicalClinical Features

• 01Painless slow-growing swelling (low grade) — may mimic mucocele on palate
• 02Rapidly growing painful mass with fixation, facial nerve palsy (high grade)
• 03Fluctuant bluish palatal swelling common

§ differentialDifferential Diagnosis

• 01Pleomorphic adenoma
• 02Mucocele (minor glands)
• 03Adenoid cystic carcinoma
• 04SCC

§ histopathHistopathology

• 01Mixture of mucous (goblet), intermediate and epidermoid cells
• 02Cystic spaces (low grade) → solid sheets with atypia (high grade)
• 03Mucicarmine and PAS-diastase stain mucous cells

§ investigationsInvestigations

• 01MRI (soft-tissue detail, perineural spread)
• 02FNAC / core biopsy
• 03CT chest for staging

§ ihcIHC / Special Stains

• 01CK7+, p63 in epidermoid cells
• 02MAML2 FISH for confirmation

§ classificationClassification

• 01Grading systems: AFIP, Brandwein, MSK — based on cystic component, invasion, necrosis, mitoses, perineural spread
• 02Low, intermediate, high grade

§ treatmentTreatment

• 01Wide local excision with clear margins
• 02Parotid: superficial or total parotidectomy with facial nerve preservation
• 03Neck dissection for high-grade / cN+
• 04Adjuvant radiotherapy for high-grade, positive margins, perineural or vascular invasion
• 05Chemotherapy for palliation

§ complicationsComplications

• 01Facial nerve injury
• 02Recurrence (high grade)
• 03Distant metastases (lung, bone) in high-grade

§ prognosisPrognosis

5-year survival: low grade >90%, intermediate ~70%, high grade 30–50%.

§ examKey Examination Points

• 01Bluish palatal swelling in adult → not a mucocele until proven otherwise
• 02Always image before biopsy of parotid mass

§ revisionQuick Revision Summary

• 01MAML2 fusion · commonest paediatric salivary malignancy · grade determines prognosis

§ vivaBDS Viva Questions

• 01Diagnostic translocation of MEC?
• 02Grading criteria?
• 03Approach to parotid MEC?

§ mcqsMCQs — Assessment (3)

§ relatedRelated Diseases

References

1. WHO Head & Neck Tumours 2022