Table of Contents
Definition / general | Essential features | Epidemiology | Pathophysiology | Etiology | Clinical features | Radiology images | Prognostic factors | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Molecular / cytogenetics description | Differential diagnosis | Board review style question #1 | Board review style answer #1Cite this page: Wei S. Mucoepidermoid carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/thyroidMuco.html. Accessed January 21st, 2025.
Definition / general
- Rare low grade malignant epithelial neoplasm with epidermoid and mucinous components (WHO: Pathology and Genetics of Tumours of Endocrine Organs, 3rd Edition, 2004)
- Two variants of mucoepidermoid carcinoma in thyroid: mucoepidermoid carcinoma (discussed in this section) and sclerosing mucoepidermoid carcinoma with eosinophilia
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
- Can arise from metaplastic dedifferentiation of papillary thyroid carcinoma, follicular carcinoma or oncocytic carcinoma (Thyroid 2012;22:205)
- May arise from thyroid follicular epithelium based on molecular studies (Clin Endocrinol (Oxf) 2002;57:551) or from solid cell nests based on ciliated epithelium (Pathol Int 2008;58:741)
Etiology
- May be associated with radiation exposure
Clinical features
- Euthyroid with painless "cold / hypofunctioing" mass in the thyroid gland
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
- 29 year old woman with follicular variant of papillary carcinoma (Am J Surg Pathol 1995;19:1209)
- 35 year old man with papillary carcinoma with mucoepidermoid differentiation (Am J Clin Pathol 1991;95:175)
- 50 year old man with composite follicular variant of papillary carcinoma and mucoepidermoid carcinoma (J Korean Med Sci 2010;25:1683)
- 86 year old man with composite mucoepidermoid carcinoma and columnar cell variant of papillary thyroid carcinoma (Int J Surg Pathol 2016;24:336)
- 91 year old woman with a rapidly growing mass of the left upper neck (Case Rep Endocrinol 2012;2012:862545)
- Case with papillary carcinoma with mucoepidermoid differentiation (Arch Pathol Lab Med 1996;120:397)
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
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
Images hosted on other servers:
Cytology description
- Epidermoid cells and mucus secreting cells with background cell debris or mucin
Positive stains
- Focally positive for Thyroiglobulin and TTF1
- Cytokeratin, CAM 5.2, CEA (polyclonal), intracytoplasmic mucin stains with Alcian blue and mucicarmine
Negative stains
Molecular / cytogenetics description
- Can demonstrate t(11;19) and CRTC1 / MAML2 fusion transcript (Genes Chromosomes Cancer 2007;46:708) and have common origin with Warthin tumor (Genes Chromosomes Cancer 2008;47:309)
Differential diagnosis
- Anaplastic carcinoma: highly malignant carcinoma with necrosis, can have squamous component
- CASTLE: squamoid cells with variable amount of lymphocytes without eosinophils, CD5+ CD117+, can have mucin
- Direct extension or metastasis of salivary mucoepidermoid carcinoma: different primary site
- Sclerosing mucoepidermoid carcinoma with eosinophilia: sclerosis and brisk infiltrate of eosinophils
- Solid cell nests and squamous metaplasia: confined to lateral and upper portion of thyroid lobes; no atypia and invasion, can have cystic change with luminal mucin, however, no mucin secreting cells / mucocytes
- Squamous cell carcinoma: sheets of highly atypical squamous cells with necrosis, no mucin, no eosinophils
Board review style question #1
Which statement is not true for mucoepidermoid carcinoma of thyroid?
- Comedo necrosis and psammoma bodies may be seen
- Foci of associated papillary thyroid carcinoma are often seen
- Lymph nodes metastases, extrathyroidal invasion are common
- Mucoepidermoid carcinoma of thyroid is associated with lymphocytic thyroiditis
- 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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Reference: Mucoepidermoid