Table of Contents
Definition / general | Clinical features | Prognostic factors | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Cytology images | Positive stains | Electron microscopy description | Electron microscopy images | Molecular / cytogenetics description | Differential diagnosisCite this page: Handra-Luca A. Mucoepidermoid carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/salivaryglandsMEC.html. Accessed December 13th, 2019.
Definition / general
- Cords, sheets and clusters of mucous, squamous, intermediate and clear cells
- Most common malignant tumor in salivary glands
- Also most common radiation induced neoplasm
Clinical features
- 2/3 occur in parotid gland; also in palate
- Wide age range, mean 49 years, range 15 - 86 years, no gender predominance
- Low grade: 15% recur, 5 year survival 90 - 98%, usually stage I
- High grade: 25% recur, 5 year survival 50 - 56%, deaths usually within first 5 years
- Note: significant grading disparity exists between pathologists (Am J Surg Pathol 2001;25:835)
AFIP point system:
- 2 points if < 20% intracystic component
- 2 points if neural invasion
- 3 points if necrosis
- 3 points if 4+ mitotic figures/10 HPF
- 4 points if anaplasia
- Low grade if total score is 0 - 4 points, intermediate grade if 5 - 6 points, high grade if 7+ points
Prognostic factors
- Poor prognostic factors: older age, male, submandibular gland, extraglandular extension, vascular invasion, necrosis, high mitotic rate, high histologic grade
Case reports
- 4 year old boy with soft tissue mass in cheek (Case of the Week #346)
- 55 year old man with low grade parotid tumor and dedifferentiation (Hum Pathol 2003;34:1068)
Treatment
- Complete excision, possibly radiation therapy
Gross description
- Low grade: well circumscribed with gray-white, mucin filled cysts
Microscopic (histologic) description
- Cords, sheets and clusters of mucous, squamous, intermediate and clear cells
- Low to high grade, although even high grade tumors lack marked nuclear atypia, frequent mitotic figures or extensive necrosis
- Occasional focal sebaceous cells, goblet type cells, oncocytic change, inflammatory reaction to extravasated mucin or keratin
- No squamous cell carcinoma in situ
- Low grade: mucinous and intermediate cells with bland nuclei form glandular spaces
- High grade: solid and infiltrative growth pattern of atypical epidermoid and intermediate cells with cytoplasmic clearing and small number of mucinous cells; < 20% intracystic component
Microscopic (histologic) images
Cytology images
Electron microscopy description
- Mixed luminal epithelial cells and myoepithelial cells
Molecular / cytogenetics description
- Associated with t(11;19)(q14-21;p12-13)
Differential diagnosis
- Adenosquamous carcinoma: has anaplastic nuclear features
- Metastatic carcinoma
- Necrotizing sialometaplasia
- Poorly differentiated adenocarcinoma
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