Thyroid & parathyroid

Other uncommon thyroid carcinomas

Mucoepidermoid carcinoma



Last author update: 1 June 2017
Last staff update: 29 August 2023

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PubMed Search: Mucoepidermoid carcinoma [title] thyroid

Shuanzeng (Sam) Wei, M.D., Ph.D.
Zubair W. Baloch, M.D., Ph.D.
Page views in 2024 to date: 575
Cite this page: Wei S. Mucoepidermoid carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/thyroidMuco.html. Accessed March 28th, 2024.
Definition / general
Essential features
  • Rare low grade malignant epithelial neoplasm with epidermoid and mucinous components
Epidemiology
  • 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
Pathophysiology
Etiology
  • 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
lesion

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
Treatment
  • 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 cells



Images hosted on other servers:

Partially solid, glandular and papillary

Squamoid nests and
mucin secreting
component

Transition from follicular
variant of papillary carcinoma
to mucoepidermoid carcinoma

Immunohistochemistry
of TTF1 and
thyroglobulin

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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