High Yield Info. No fluff. Here's some of the key features to know (for the boards)...
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
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
Vascular invasion (NOTE: Perineural invasion is common)
High mitotic rate
High histologic grade
Surgical excision is 1st line of treatment. +/- radiation for local control
KEY HISTOLOGY FINDINGS
Well-circumscribed nodules with indistinct borders- can be predominantly cystic to predominantly solid
Mucoepidermoid Carcinoma is composed of an admixture of 3 cell types:
Mucocytes (mucin forming cuboidal cells with bland nuclei and occasional small nucleolus- NOTE: Mucin filled microcysts & clear cell change are common with vacuolated cytoplasm)
Epidermoid cells (polyhedral atypical cells with dense cytoplasm)
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
ASSIGN 3 POINTS:
4+ mitotic figures per 10 HPF
ASSIGN 4 POINTS:
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)
(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
Adenosquamous carcinoma: Higher grade tumor with anaplastic features
Metastatic or Poorly differentiated (adeno)carcinoma: Review clinical history
And there you have it...
Handra-Luca A. Mucoepidermoid carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/salivaryglandsMEC.html. Accessed July 20th, 2019.
PathPresenter.net (links provided above)