HIGH YIELD: Mucoepidermoid Carcinoma

High Yield Info. No fluff. Here's some of the key features to know (for the boards)...



GENERAL INFO


Most common... malignant tumor of salivary glands
Most common... radiation-induced neoplasm
A "Muco-Ep" is basically is a tumor that has both adeno/glandular (MUCOus) + squamous (EPIDERMOID) components


HIGH YIELD ASSOCIATIONS:

  • MAML2 gene rearrangement

  • t(11;19)(q14-21;p12-13)


TYPICAL CLINICAL PICTURE:

  • Elderly patient presents an elevated plaque on the H&N

  • Most commonly arises in the parotid gland or palate

POOR PROGNOSTIC INDICATORS

  • Old age

  • Male

  • Submandibular gland

  • Extraglandular extension

  • Vascular invasion (NOTE: Perineural invasion is common)

  • Necrosis

  • High mitotic rate

  • High histologic grade

TREATMENT

  • Surgical excision is 1st line of treatment. +/- radiation for local control

KEY HISTOLOGY FINDINGS


- EXAMINE THE VIRTUAL SLIDE -

  • Well-circumscribed nodules with indistinct borders- can be predominantly cystic to predominantly solid



Mucoepidermoid Carcinoma is composed of an admixture of 3 cell types:

  1. Mucocytes (mucin forming cuboidal cells with bland nuclei and occasional small nucleolus- NOTE: Mucin filled microcysts & clear cell change are common with vacuolated cytoplasm)

  2. Epidermoid cells (polyhedral atypical cells with dense cytoplasm)

  3. Intermediate cells (mixture between the 2)

In the images below, note the cords, sheets & clusters of mucous, squamous, intermediate and clear cells.


  • Background with chronic inflammation

  • Deep dermal infiltration with perineural invasion is common


GRADING MUCO-EPs (AFIP Point System)


The presence of cellular pleomorphism, mitoses, and necrosis vary with grade. There is very low concordance between pathologists, but the AFIP point system can be helpful to determine whether a MEC is low- intermediate- or high grade.


Examine the tumor and assign "points" if any of the following features are identified:


ASSIGN 2 POINTS:

  • <20% intracystic component

  • Neural invasion

ASSIGN 3 POINTS:

  • Necrosis

  • 4+ mitotic figures per 10 HPF

ASSIGN 4 POINTS:

  • Anaplasia

TOTAL SCORE = 0-4 LOW GRADE
TOTAL SCORE = 5-6 INTERMEDIATE GRADE
TOTAL SCORE = 7+ HIGH GRADE

Check out some examples below; Clicking on the image or the link will open the virtual slide on PathPresenter.net.


LOW GRADE; SCORE = 0-4 (Click to view slide)

INTERMEDIATE GRADE; SCORE = 5-6 (Click to view slide)

HIGH GRADE; SCORE = 7+ (Click to view slide)


  • Variants: clear cell, oncocytic cells

  • Can be assocainted with tumor-associated lymphoid proliferation (TALP)

ANCILLARY STUDIES

(EX: ADDITIONAL TESTS TO CLUE YOU IN TO THE DIAGNOSIS)

  • LOW GRADE: CK7, CK14, Antimitochondrial antibodies

  • Ki-67 stain & Mucicarmine could be helpful

  • Electron microscopy (rarely done)- Mixed luminal epithelial cells surrounded by myoepithelial cells


DIFFERENTIAL DIAGNOSES

  • Adenosquamous carcinoma: Higher grade tumor with anaplastic features

  • Metastatic or Poorly differentiated (adeno)carcinoma: Review clinical history

  • Necrotizing sialometaplasia

And there you have it...


Reference:

https://wiydx.com/DermSection/DermCase/Histological/EBA7B092-4C3B-4889-BAD5-A16B969D0A87


Handra-Luca A. Mucoepidermoid carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/salivaryglandsMEC.html. Accessed July 20th, 2019.


PathPresenter.net (links provided above)

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DISCLAIMER: THIS WEBSITE DOES NOT PROVIDE MEDICAL ADVICE

These posts contain high yield information collected from various educational resources including textbooks, journal articles, educational websites and more. They are intended for educational use only and should NOT be taken as medical advice. I strongly believe the spreading of knowledge and depth of learned information should be encouraged in today's society rather than coveted. Membership is required to view these posts  and should be used solely for educational purposes only.