Lung tumor
Salivary gland type
Mucoepidermoid carcinoma

Topic Completed: 1 May 2018

Minor changes: 23 October 2019

Copyright: 2003-2019,, Inc.

PubMed Search: Mucoepidermoid carcinoma [title] lung tumor AND (free full text[sb])

Roseann Wu, M.D., M.P.H.
Page views in 2019: 6,071
Page views in 2020 to date: 4,045
Cite this page: Wu R. Mucoepidermoid carcinoma. website. Accessed August 8th, 2020.
Definition / general
  • Low grade or high grade salivary gland type tumor with mucous secreting cells, squamous cells and intermediate cells
  • Distinguished from other lung cancers by central or peribronchial location, mucous cells, lack of keratinization, expression of p63 and MAML2 rearrangement (Mod Pathol 2014;27:1479)
Essential features
  • Most common salivary gland type tumor in the lung, tends to arise centrally
  • Similar morphology to mucoepidermoid carcinoma arising in the head and neck with a mixture of mucous cells, squamous cells and intermediate cells; must exclude metastasis
  • Strong association with t(11;19)(q21;p13) and MAML2 rearrangement by fluorescence in situ hybridization (FISH)
  • Squamous component stains with p63 and p40
  • Same diagnostic terminology as used in the salivary gland
ICD coding
  • C33 Malignant neoplasm of trachea
  • C34.00 Malignant neoplasm of unspecified main bronchus
  • C34.01 Malignant neoplasm of right main bronchus
  • C34.02 Malignant neoplasm of left main bronchus
  • Code more peripheral lesions depending on specific lobe, laterality and extent
  • Any lung lobe, usually in relation to large bronchi
  • May arise from submucosal bronchial glands
Clinical features
  • Large central tumors cause obstructive symptoms such as dyspnea, cough, hemoptysis or pneumonia
  • Peripheral lesions may be asymptomatic
  • Bronchoscopy may be used to directly visualize and sample an endobronchial tumor
  • Diagnosis may be difficult in small biopsies; may mimic primary non small cell lung carcinoma
Radiology description
  • Can be difficult to detect on imaging due to small size of tumor, endobronchial location, association with pneumonia or atelectasis (Arch Pathol Lab Med 2007;131:1400)
  • On CT, markedly enhanced homogeneous central bronchial nodule / mass suggests low grade mucoepidermoid carcinoma (MEC); high grade MEC tends to be peripheral with poorly defined margins, lobular, heterogeneous with less enhancement (AJR Am J Roentgenol 2015;205:1160)
  • Uncommon findings included cavitation, diffuse thickening or spiculation (Clin Imaging 2012;36:8)
Radiology images

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Heterogeneously enhancing lesion

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Mass shadow measuring 30 mm

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Mass in right upper lobe and left hilum

Prognostic factors
Case reports
Clinical images

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Well circumscribed endobronchial tumor

Gross description
  • Polypoid, exophytic growth or sessile tumor in major bronchi, may be > 5 cm
  • Generally well circumscribed and smooth with tan to yellow cut surface
  • May be solid or cystic and potentially show glistening mucoid material
Gross images

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Mucoepidermoid carcinoma of airways

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Tumur in middle lobe bronchus

Microscopic (histologic) description
  • Low grade has more cysts and mucous cells; high grade has more solid or nested growth, atypia, mitotic activity, necrosis, hemorrhage
  • Mucus secreting cells, squamoid cells without significant keratinization, intermediate type cells
  • Mucus secreting cells usually large with light blue-gray mucinous cytoplasm; variants include columnar, goblet, cuboidal, clear or oncocytic cells (Arch Pathol Lab Med 2007;131:1400)
  • Squamous cells show intercellular bridges but no keratin whorls or pearls; intermediate cells usually polygonal with bland nucleus (Arch Pathol Lab Med 2007;131:1400)
  • May show areas of papillary growth or spindled cells
  • May have dense lymphoplasmacytic infiltrate (Am J Surg Pathol 2005;29:407)
  • Lack in situ carcinoma of overlying epithelium
Microscopic (histologic) images

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Contributed by Roseann Wu, M.D., M.P.H.
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Low grade mucoepidermoid carcinoma - 20x

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Low grade MEC mucicarmine stain - 20x

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High grade mucoepidermoid carcinoma - 10x

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High grade mucoepidermoid carcinoma - 20x

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MEC of lung

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Large mucous filled glands lined by goblet cells, respiratory epithelium and squamous epithelium

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Stroma infiltrated by inflammatory cells

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EGFR seen in squamous and intermediate cells

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Pulmonary MEC

MEC-like pulmonary carcinoma

Virtual slides

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Mucoepidermoid carcinoma of the lung, from Juan Rosai’s Collection of Surgical Pathology Seminars

Cytology description
  • Mixture of squamoid cells, mucous cells and intermediate cells
  • Diff-Quik with numerous tight clusters of relatively small and bland cells with well defined but scant cytoplasm, central round and uniform nuclei with small nucleoli; second population of glandular appearing cells with cytoplasmic vacuoles with mucin, focal extracellular metachromatic mucinous material (Diagn Cytopathol 2013;41:1096)
Positive stains
Negative stains
Molecular / cytogenetics description
  • MAML2 rearrangement most common molecular genetic event, found more in low grade tumors (PLoS One 2015;10:e0143169)
  • May stain with epidermal growth factor receptor (EGFR) but does not show the mutation or alterations in copy number (Mod Pathol 2008;21:1168)
  • Reciprocal translocations, including t(1;11)(p22;q13) with overexpression of cyclin D1, t(11;19)(q14-21;p12) and t(11;19)(q21;p13) which encodes MECT1-MAML2 (MECT1 also known as CRTC1) (Arch Pathol Lab Med 2007;131:1400)
Molecular / cytogenetics images

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MAML2 rearrangement by FISH

Differential diagnosis
Additional references
Board review style question #1
    Rearrangement of which gene would support the diagnosis of mucoepidermoid carcinoma of the lung?

  1. APC
  2. BRAF
  3. MAML2
  4. PIK3CA
  5. PLAG1
Board review answer #1
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