Mucoepidermoid carcinoma

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Mucoepidermoid carcinoma, abbreviated MEC, the is the most common malignant neoplasm of the salivary gland.

Mucoepidermoid carcinoma
Diagnosis in short

Mucoepidermoid carcinoma. H&E stain.
LM mucous cells (abundant fluffy cytoplasm and large mucin vacuoles - nucleus distorted by mucin vacuole, cells may be scarce); epidermoid cells (non-keratinized, polygonal squamoid cell with clear or oncocytic cytoplasm); architecture - cystic (low grade) or solid (high grade)
LM DDx squamous cell carcinoma of the head and neck, adenosquamous carcinoma
Stains mucous cells: alcian blue stain +ve, mucicarmine stain +ve
Molecular t(11;19)(q21;p13)
Gross solid, cystic or both
Site salivary gland, classically parotid gland
Signs mass lesion
Prevalence most common malignant salivary gland tumour, generally uncommon

General

  • Most common malignant neoplasm of salivary gland in all age groups.[1]
  • Female:male ~= 3:2.
  • Site: parotid > submandibular.

Gross

  • Cystic or solid, usu. a mix of both.

Microscopic

Features:

  • Architecture:[2]
    • Cystic (low grade).
    • Solid (high grade).
  • Mucous cells with abundant fluffy cytoplasm and large mucin vacuoles - key feature.
    • Nucleus distorted by mucin vacuole.
    • Mucous cell may be scarce - more difficult to diagnose.
  • Epidermoid cells:
    • Non-keratinized, polygonal squamoid cell with clear or oncocytic cytoplasm.
      • Clear cells contain glycogen (PAS +ve, PAS-D -ve).

Notes:

  • The classic description - composed of 3 cell types: epidermoid, intermediate, and mucin producing.[3]
    • "Intermediate cells" are described in textbooks. Weinreb thinks they are a pretty much a myth.[4]
  • Mucin vacuoles may be rare; in a superficial glance -- it may mimic squamous cell carcinoma.
  • The thought of high-grade MEC should prompt consideration of squamous cell carcinoma.

DDx:[5]

Images

  • Mucoepidermoid carcinoma 2. (WC)

  • Mucoepidermoid carcinoma 3. (WC)

  • Mucoepidermoid carcinoma - 2 - intermed. mag. (WC/Nephron)

  • Mucoepidermoid carcinoma - 2 - high mag. (WC/Nephron)

  • Mucoepidermoid carcinoma - 2 - very high mag. (WC/Nephron)

www:

Subtypes

  • Conventional.
  • Oncocytic.
    • Definition: composed of 50% oncocytes.
    • Good outcome.[6]
  • Clear cell.
  • Unicystic (cystadenocarcinoma).
    • Based on the gross. (???)
  • Sclerosing MEC +/- eosinophilia.
    • Rare.

Grading

General:

  • Two competing system exist:

Notes:

  • Both systems have their pros and cons.
  • Weinreb uses the AFIP system with a slight modification.

AFIP

  1. Low cystic content (<20%) - 2 points.
  2. Perineural invasion - 2 points.
  3. Necrosis - 3 points.
  4. Mitoses > 4 per 10 HPFs (HPF not defined in paper - see HPFitis) - 3 points.
  5. Anaplasia - 4 points.

Scoring:

  • Low grade = 0-4 points.
  • Intermediate grade = 5-6 points.
  • High grade = 7+ points.
Weinreb modification

Weinreb looks for the following:

  • Tumour invades in small nests/islands - 2 points.
    • If applicable, the two points are added to the AFIP score.
    • The tumour is graded using the AFIP (scoring) cut points -- see above.

Notes:

  • It seems pointless to memorize this but it is occasionally asked on exams.
    • How to remember: think of the Nottingham grading system (architecture, mitoses, nuclear grade) + necrosis + LVI.

Stains

Mucous cells:

  • Alcian blue +ve.
  • Mucicarmine +ve.

Molecular

  • t(11;19)(q21;p13) -- MECT1-MAML2 fusion.[9][10]
    • Present in ~65% of MECs.
    • Presence assoc. with low-grade MEC (vs. high-grade MEC) & favourable prognosis.
    • Not seen in tumours that are in the DDx of MEC.

See also

References

  1. ↑ URL: http://path.upmc.edu/cases/case715/dx.html. Accessed on: 2 February 2012.
  2. ↑ URL: http://moon.ouhsc.edu/kfung/jty1/opaq/PathQuiz/D2A001-PQ01-M.htm. Accessed on: 19 October 2010.
  3. ↑ Lennerz, JK.; Perry, A.; Mills, JC.; Huettner, PC.; Pfeifer, JD. (Jun 2009). "Mucoepidermoid carcinoma of the cervix: another tumor with the t(11;19)-associated CRTC1-MAML2 gene fusion.". Am J Surg Pathol 33 (6): 835-43. doi:10.1097/PAS.0b013e318190cf5b. PMID 19092631.
  4. ↑ IW. 10 January 2011.
  5. ↑ 5.0 5.1 Mokhtari, S.; Mokhtari, S. (2012). "Clinical features and differential diagnoses in laryngeal mucoepidermoid carcinoma.". Clin Med Insights Pathol 5: 1-6. doi:10.4137/CPath.S8435. PMID 22262946.
  6. ↑ Weinreb I, Seethala RR, Perez-Ordoñez B, Chetty R, Hoschar AP, Hunt JL (March 2009). "Oncocytic mucoepidermoid carcinoma: clinicopathologic description in a series of 12 cases". Am. J. Surg. Pathol. 33 (3): 409–16. doi:10.1097/PAS.0b013e318184b36d. PMID 18971778.
  7. ↑ Goode RK, Auclair PL, Ellis GL (April 1998). "Mucoepidermoid carcinoma of the major salivary glands: clinical and histopathologic analysis of 234 cases with evaluation of grading criteria". Cancer 82 (7): 1217–24. PMID 9529011.
  8. ↑ Brandwein MS, Ivanov K, Wallace DI, et al. (July 2001). "Mucoepidermoid carcinoma: a clinicopathologic study of 80 patients with special reference to histological grading". Am. J. Surg. Pathol. 25 (7): 835–45. PMID 11420454.
  9. ↑ Tonon G, Modi S, Wu L, et al. (February 2003). "t(11;19)(q21;p13) translocation in mucoepidermoid carcinoma creates a novel fusion product that disrupts a Notch signaling pathway". Nat. Genet. 33 (2): 208–13. doi:10.1038/ng1083. PMID 12539049.
  10. ↑ Seethala RR, Dacic S, Cieply K, Kelly LM, Nikiforova MN (August 2010). "A reappraisal of the MECT1/MAML2 translocation in salivary mucoepidermoid carcinomas". Am. J. Surg. Pathol. 34 (8): 1106–21. doi:10.1097/PAS.0b013e3181de3021. PMID 20588178.
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