Salivary glands
Primary salivary gland neoplasms
Malignant
Mucoepidermoid carcinoma


Minor changes: 19 April 2021

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PubMed Search: Mucoepidermoid carcinoma[TI] salivary gland[TI]

Saeed Asiry, M.D.
Rema A. Rao, M.D.
Page views in 2020: 43,712
Page views in 2021 to date: 33,934
Cite this page: Asiry S, Rao RA. Mucoepidermoid carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/salivaryglandsMEC.html. Accessed August 2nd, 2021.
Definition / general
  • Malignant glandular epithelial neoplasm characterized by mucous, intermediate and epidermoid cells, with columnar, clear cell or oncocytoid features
Essential features
  • Malignant epithelial neoplasm
  • Characterized by mucous, intermediate and epidermoid cells, with columnar, clear cell or oncocytoid features
  • Most common malignant salivary gland neoplasm in both adults and children
  • Prognosis influenced by tumor stage, tumor site, surgical margins (WHO 2017)
  • Associated with a specific translocation t(11;19)(q14-21;p12-13) with CRTC1(MECT1)-MAML2 fusion
Terminology
  • Mucoepidermoid carcinoma (MEC)
  • Not recommended: mucoepidermoid tumor
ICD coding
  • ICD-O: 8430/3 - Mucoepidermoid carcinoma
  • ICD-10 (depends on site):
    • C08.0 - Malignant neoplasm of submandibular gland
    • D48.7 - Neoplasm of uncertain behavior of other specified sites
    • C07 - Malignant neoplasm of parotid gland
    • C08.9 - Malignant neoplasm of major salivary gland, unspecified
Epidemiology
Sites
Etiology
Clinical features
Diagnosis
  • Preoperative assessment (radiology) may consist of:
    • Ultrasonography (USG) for small tumors in major salivary glands
    • Larger recurrent tumors: CT imaging for bone involvement, MRI for soft tissue delineation (Semin Radiat Oncol 2012;22:245)
    • Evidence of (18)-fluorodeoxyglucose positron emission tomography CT in locoregionally advanced tumors (Nucl Med Commun 2013;34:211)
  • Preoperative assessment (fine needle aspiration):
Radiology description
  • Influenced by tumor size, location and possibly tumor grade
  • Ultrasonography:
    • Typically a well circumscribed hypoechoic lesion, with a partial or completely cystic appearance against a relatively hyperechoic normal parotid gland
  • CT:
    • Lower grade tumors are well circumscribed with cystic component (see Radiology images)
    • Enhancing solid component and calcifications occasionally seen
    • Higher grade tumors are solid and show poorly defined, infiltrative margins
  • MRI:
    • Low grade tumors are similar in appearance to a pleomorphic adenoma
    • Higher grade tumors are solid, with a lower signal on T2 and poorly defined margins
  • Reference: Radiopaedia: Mucoepidermoid Carcinoma of Salivary Glands [Accessed 8 January 2021]
Radiology images

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Parotid mucoepidermoid carcinoma, CT

Parotid mucoepidermoid carcinoma, CT

Prognostic factors
  • Adults:
    • Excellent prognosis, with approximately 98.8% 5 year survival rate in low grade and 97.4% in intermediate grade tumors
    • About 67% 5 year survival rate for high grade tumors
  • Children:
    • 5 year survival of 98%, as they predominantly present with low to intermediate grade tumors
  • Negative prognostic variables
    • High clinical stage / histologic grade
    • Tumor arising in the submandibular gland: lymph node metastases common
    • Positive surgical margins
    • Extraparenchymal extension
    • Nodal / distant metastases
    • Negative CRTC1-MAML2 fusion (Am J Surg Pathol 2019;43:885)
    • Increased expression of MUC1
  • References: J Stomatol Oral Maxillofac Surg 2020;121:713, Wenig: Atlas of Head and Neck Pathology, 3rd Edition, 2016
Case reports
Treatment
  • Complete surgical resection
    • Conservative approach for stage I and stage II tumors
    • Wide excision with wide margin for high grade tumors or tumors with positive margins
  • Neck lymph node dissection (depends on nodal status and histologic grade)
  • Adjuvant radiotherapy and chemotherapy might be considered for higher grade tumors
  • Reference: J Stomatol Oral Maxillofac Surg 2020;121:713
Gross description
Gross images

Contributed by Kelly Magliocca D.D.S., M.P.H.

Cut surface, high grade

Frozen section description
Frozen section images

Contributed by Rema A. Rao, M.D. and Saeed Asiry, M.D.
Positive margin for tumor Positive margin for tumor Positive margin for tumor

Positive margin for tumor

Microscopic (histologic) description
  • Solid, cystic or mixed growth patterns
  • Can show papillary or glandular growth pattern
  • Areas suggesting a capsule can be seen in low grade mucoepidermoid carcinoma
  • Varying proportions of epidermoid cells, intermediate cells and mucocytes
  • Solid nests, sheets or cords of epidermoid cells
  • Overt keratinization is rare
  • Mucous cells embedded in epidermoid cell nests or lining cystic spaces
  • Intermediate cells found within epidermoid cell nests or forming separate nests
  • Background stromal sclerosis
  • Luminal or extracellular pools of mucin may be present
  • Mitosis, necrosis and pleomorphism more commonly seen in high grade tumors
  • Limited number of mucocytes and cystic spaces in high grade tumors
  • Perineural and lymphovascular invasion possible (Wenig: Atlas of Head and Neck Pathology, 3rd Edition, 2016)
  • Focal clear cell changes can occur due to accumulation of glycogen
  • Histologic variants: clear cell, oncocytic and sclerosing (Am J Surg Pathol 1999;23:523)
  • Reference: J Stomatol Oral Maxillofac Surg 2020;121:713

Histopathologic grading:
  • 4 histologic grading systems (2 quantitative and 2 qualitative)
  • 2 different morphologic quantitative point systems, although histologic grading using any grading system appears to be inconsistent (Am J Surg Pathol 2019;43:885)
  • Significant grading disparity between pathologists (Am J Surg Pathol 2019;43:885)
  • Armed Forces Institute of Pathology (AFIP) grading scheme (quantitative) (Am J Surg Pathol 2019;43:885)
    • Criteria:
      • Intracystic component less than 20% (2)
      • Neural invasion (2)
      • Necrosis (3)
      • 4 or more mitoses (3)
      • Anaplasia (4)
    • Grade:
      • Low grade (0 - 4)
      • Intermediate grade (5 - 6)
      • High grade (7 or more)
  • Brandwein et al. grading scheme (quantitative) (Am J Surg Pathol 2001;25:835)
    • Criteria:
      • Intracystic component less than 25% (2)
      • Tumor front invades in small nests and islands (2)
      • Pronounced nuclear atypia (2)
      • Lymphovascular invasion (3)
      • Bony invasion (3)
      • 4 or more mitoses (3)
      • Perineural invasion (3)
      • Necrosis (3)
    • Grade:
      • Low grade (0)
      • Intermediate grade (2 - 3)
      • High grade (4 or more)
  • Modified Healy grading system (qualitative)
    • Low grade
      • Macro and microcysts
      • Rare intermediate cells
      • Rare mitotic figures
      • Absent or minimal nuclear pleomorphism
      • Well circumscribed tumor with broad edges
      • Extravasated mucin and fibrotic stroma present
    • Intermediate grade
      • Microcysts and solid component
      • More intermediate cells
      • Few mitotic figures
      • Slight nuclear pleomorphism
      • Uncircumscribed tumor
      • Fibrotic stroma separating tumor nests
    • High grade
      • Predominantly solid, with or without microcysts
      • Perineural invasion present
      • Lymphovascular invasion present
      • Surrounding soft tissue invasion present
      • Many mitotic figures
      • Nuclear pleomorphism, including presence of prominent nucleoli
      • Predominance of intermediate cells
      • Desmoplastic stoma
  • Memorial Sloan Kettering Cancer Center (MSKCC) grading system (qualitative)
    • Low grade
      • Predominantly cystic growth pattern (> 80%)
      • 0 - 1 mitotic figures/10 high power fields (HPF)
      • Well circumscribed
      • No necrosis
    • Intermediate grade
      • Predominantly solid growth pattern
      • 2 - 3 mitotic figures/10 high power fields (HPF)
      • Well circumscribed or infiltrative
      • No necrosis
    • High grade
      • Any growth pattern but usually solid
      • ≥ 4 mitotic figures/10 high power fields (HPF)
      • Usually infiltrative
      • Necrosis is present
Microscopic (histologic) images

Contributed by Rema A. Rao, M.D. and Saeed Asiry, M.D.
Tumor architecture

Tumor architecture

Tumor cell types

Tumor cell types

Epidermoid cells

Epidermoid cells

Mucus cells

Mucus cells

Intermediate cells

Intermediate cells

Clear cell changes

Clear cell changes



Case #346

4 year old boy

Ki67

Mucicarmine

Virtual slides

Images hosted on other servers:
Low grade mucoepidermoid carcinoma

Low grade mucoepidermoid carcinoma

Cytology description
  • Most often graded as low grade or high grade on FNA
  • Low to intermediate grade:
    • Can be acellular or hypocellular smears
    • Extracellular mucin may be the prominent feature
    • Cystic background
    • Aggregates of epidermoid cells, intermediate cells and mucocytes
    • Epidermoid cells appear as bland cohesive flat sheets with squamoid / dense cytoplasm and well defined cellular borders
    • Predominantly mucus cells floating in extracellular mucin (low grade)
    • No keratinization seen
    • Lympocytes present in about 20% of cases and are abundant
  • High grade:
    • Highly cellular aspirates
    • High grade nuclear features with pleomorphic nuclei, prominent nucleoli
    • Intermediate cells and mucous cells are rare
    • Increased mitosis
    • Necrotic background
  • References: J Clin Diagn Res 2017;11:ER04, Cibas: Cytology - Diagnostic Principles and Clinical Correlates, 5th Edition, 2020
Cytology images

Contributed by Rema A. Rao, M.D. and Saeed Asiry, M.D.
Background mucin

Background mucin

Neoplastic cells

Neoplastic cells

Mucus cells

Mucus cells

Neoplastic cells in sheets

Neoplastic cells in sheets

Keratinizing cells

Keratinizing cells

Single keratinizing cells

Single keratinizing cells


Crowded squamous cells

Crowded squamous cells



Images hosted on other servers:

Low grade with background mucin, 2
types of cells with bland nuclear features

High grade with malignant squamous cells

Low grade and oncocytic tumors

Positive stains
Negative stains
Electron microscopy description
Molecular / cytogenetics description
Molecular / cytogenetics images

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FISH analysis of MAML2

FISH analysis of MAML2

Sample pathology report
  • Parotid gland, right, parotidectomy:
    • Mucoepidermoid carcinoma, intermediate grade (2.3 cm)
    • Three lymph nodes, negative for carcinoma (0/3).
    • Surgical margins negative for carcinoma.
    • Carcinoma 0.3 cm of closest margin, medial.
    • See synoptic report.
Differential diagnosis
Board review style question #1
Which of the following is true about mucoepidermoid carcinoma?

  1. Associated with t(12;15)(p12;q25) and ETV6-NTRK3 gene fusion
  2. Highly associated with smoking
  3. Most common malignant salivary tumor in children
  4. Positive for HER2 and AR by immunohistochemistry
  5. Prognosis is poor regardlesss of histologic grade
Board review style answer #1
C. Most common malignant salivary tumor in children

Comment Here

Reference: Mucoepidermoid carcinoma
Board review style question #2
Which of the following histologic features is more commonly seen in low to intermediate grade mucoepidermoid carcinoma?

  1. 4 or more mitoses
  2. Bone invasion
  3. Intracystic component more than 30%
  4. Necrosis
  5. Perineural invasion
Board review style answer #2
C. Intracystic component more than 30%

Comment Here

Reference: Mucoepidermoid carcinoma
Board review style question #3

The focal clear cell change seen in this mucoepidermoid carcinoma case is due to

  1. Accumulation of glycogen
  2. Accumulation of mucin
  3. Degradation of neoplastic cells
  4. Fixation artifact
  5. High grade transformation
Board review style answer #3
A. Accumulation of glycogen

Comment Here

Reference: Mucoepidermoid carcinoma
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