Thyroid & parathyroid

Other thyroid carcinoma



Topic Completed: 1 June 2017

Minor changes: 28 May 2021

Copyright: 2003-2021,, Inc.

PubMed Search: Mucoepidermoid carcinoma [title] thyroid

Shuanzeng (Sam) Wei, M.D., Ph.D.
Zubair W. Baloch, M.D., Ph.D.
Page views in 2020: 1,000
Page views in 2021 to date: 824
Cite this page: Wei S. Mucoepidermoid. website. Accessed December 2nd, 2021.
Definition / general
Essential features
  • Rare low grade malignant epithelial neoplasm with epidermoid and mucinous components
  • Affects all ages, more female than males (F/M = 2/1)
  • 0.5% of all thyroid malignant neoplasms
  • Shares most of the epidemiological features of papillary thyroid carcinoma
  • May be associated with radiation exposure
Clinical features
  • Euthyroid with painless "cold / hypofunctioing" mass in the thyroid gland
Radiology images

Images hosted on other servers:

Large tumor with
internal hypodensity

Prognostic factors
  • Good long term prognosis; can have extrathyroidal invasion and regional lymph nodes metastasis but distant metastases or death due to disease are uncommon
Case reports
  • Surgery or external beam radiation
  • Radio ablation for cases with extensive invasion
Gross description
  • Noncircumscribed, firm, white to brownish tan cut surface; may have mucoid or cystic spaces
Gross images

Images hosted on other servers:

White tan cut surface

Microscopic (histologic) description
  • Similar but not identical to mucoepidermoid carcinoma of the salivary glands
  • Nests of epidermoid and mucin producing cells (mucocytes) embedded in fibrotic tissue
  • Medium sized nuclei with pale chromatin mimicking papillary thyroid carcinoma (can show nuclear grooves and pseudoinclusions)
  • Mucocyte with clear to foamy or vacuolated cytoplasm, can have hyaline bodies (PAS+) in the cytoplasm
  • Ciliated cells may be seen
  • Can show extracellular mucin, comedo necrosis and psammoma bodies
  • Foci of associated papillary thyroid carcinoma in up to 50% of cases
  • Often with background of lymphocytic thyroiditis
  • No eosinophils
Microscopic (histologic) images

AFIP images

Solid nest with mucin producing foci

Microcystic pattern
of mucin producing

Images hosted on other servers:

Partially solid, glandular and papillary

Squamoid nests and
mucin secreting

Transition from follicular
variant of papillary carcinoma
to mucoepidermoid carcinoma

of TTF1 and

Cytology description
  • Epidermoid cells and mucus secreting cells with background cell debris or mucin
Positive stains
Negative stains
Molecular / cytogenetics description
Differential diagnosis
Board review style question #1
Which statement is not true for mucoepidermoid carcinoma of thyroid?

  1. Comedo necrosis and psammoma bodies may be seen
  2. Foci of associated papillary thyroid carcinoma are often seen
  3. Lymph nodes metastases, extrathyroidal invasion are common
  4. Mucoepidermoid carcinoma of thyroid is associated with lymphocytic thyroiditis
  5. Similar to sclerosing mucoepidermoid carcinoma with eosinophilia, it cannot have t (11;19) - CRTC1 / MAML2 rearrangement
Board review style answer #1
E. Similar to sclerosing mucoepidermoid carcinoma with eosinophilia, it cannot have t (11;19) - CRTC1 / MAML2 rearrangement. Mucoepidermoid carcinoma can have t (11;19) - CRTC1 / MAML2 rearrangement.

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Reference: Mucoepidermoid
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