Mucoepidermoid carcinoma of salivary gland

Epidemiology

The most common malignant tumour of salivary glands, it constitutes 15.5% of all salivary gland tumours and 29% of all malignancies, occurring in both major and minor salivary glands2.

Histopathology

Mucoepidermoid carcinomas are composed of varying proportions of epidermoid, glandular, mucous and intermediate cells.

Variant:

• Sclerosing mucoepidermoid carcinoma with eosinophilia. This uncommon tumour of the salivary gland resembles the tumour of the thyroid of this name. The borders are infiltrative. There is a sclerotic stroma infiltrated by chronic inflammatory cells and eosinophils. The epithelial cells are predominantly squamoid with focal keratinisation and have the cytology of a low grade carcinoma. They merge with a mucinous glandular element6.

• Oncocytic variant: characteristed by extensive oncocytic cells but also cytopalsmic mucin, mucin-filled cystic spaces or non-oncocytic islands. This type is rare6.

Various grading systems have been proposed6:

• Traditional: low, intermediate and high grade

• Evans: low or high grade based on >10% or <10% intracystic spaces (excluding areas of stroma and extravasated mucus).

• AFIP: Intracystic component <20%; score 2, neural invasion; score 2, necrosis; score 3, mitoses>=4/10HPF; score 3, anaplasia; score 4: score 0-4; low grade, score 5-6; intermediate grade, score >=7; high grade. This grading has been improved by adding lymphovascular invasion, bone invasion and invasive small tumour nests7.

Immunohistochemistry

Cytogenetics

A specific translocation has been identifed, t(11;19)(q21;p13)6. This fuses MECT1 with MAML2.

Differential diagnosis

High grade mucoepidermoid carcinoma:

• Squamous cell carcinoma. Mucoepidermoid carcinomas contain mucins, as demonstrated by Alcian blue or antibodies to MUC5AC5.

• Oncocytic variant: oncocytoma; oncocytoma comprises a pure population of concotyic cells.

Prognosis

There is a broad spectrum of aggressiveness. Outcome is dependent on tumour grade, margin status, location of the tumour and nodal status2. Negativity for MUC1 and positivity for MUC4 may be associated with a better prognosis3,5. MECT1-MAML2 fusion-positivity is associated with much less aggressive behaviour6, with a median survival of over 10 years, compared to 1.6 years for fusion-negative patients6. The AFIP grading predicts outcome for intra-oral and parotid tumours: submandibular tumours have a significant metastatic potential irrespective of grade6.

References

1 Chu, P. G. and L. M. Weiss (2002). "Keratin expression in human tissues and neoplasms." Histopathology 40(5): 403-39. (Summary data from multiple papers)

2 Perez-Ordonez B. Selected topics in salivary gland tumour pathology. Current Diagnostic Pathology2003;9:355-365.

3 Handra-Luca A, Lamas G, Bertrand JC, et al. MUC1, MUC2, MUC4, and MUC5AC expression in salivary gland mucoepidermoid carcinoma: diagnostic and prognostic implications. Am J Surg Pathol 2005; 29:881-9

4 Alos L, Lujan B, Castillo M. Expression of mucins (MUC1, MUC2, MUC5AC, MUC6) in mucoepidermoid carcinoma of salivary glands. Modern Pathology 2004;17:926 (abstract)

5 Hotte SJ, Winquist EW, Lamont E, et al. Imatinib mesylate in patients with adenoid cystic cancers of the salivary glands expressing c-kit: a Princess Margaret Hospital phase II consortium study. J Clin Oncol 2005; 23:585-90

6 Cheuk W,Chan JK. Advances in salivary gland pathology. Histopathology 2007; 51:1-20

7 Brandwein MS, Ivanov K, Wallace DI, et al. Mucoepidermoid carcinoma: a clinicopathologic study of 80 patients with special reference to histological grading. Am J Surg Pathol 2001; 25:835-45

8 Meer S,Altini M. CK7+/CK20- immunoexpression profile is typical of salivary gland neoplasia. Histopathology 2007; 51:26-32

This page last revised 4.8.2007.

©SMUHT/PW Bishop