Pleomorphic Adenoma: Benign neoplasm composed of cells demonstrating epithelial and myoepithelial differentiation, that often includes mesenchymal-appearing elements (myxoid, hyaline, chondroid, and osseous areas). 

Key Combined Findings for Diagnosis:

• Admixture of epithelial, myoepithelial, and stromal components
• Circumscribed/Encapsulated

Histologic Findings:

• ​​In major salivary glands 
  • ​Encapsulated, but fibrous capsule varies in thickness and may be thin or even absent
  • Can be multinodular
  • Capsular extension not diagnostic for carcinoma
• In minor salivary glands 
  • Generally not encapsulated, but typically circumscribed or well demarcated
  • ​Extension and involvement of surface epithelium not diagnostic feature for malignancy
• ​Admixture of epithelial, myoepithelial, and stromal components
  • ​Epithelial (Inner) Layer cells: make tubules and appear flattened, cuboidal, or columnar with round to oval nuclei and a variable amount of cytoplasm appearing eosinophilic to amphophilic
  • Myoepithelial (Outer) Layer cells: may be spindle-shaped, plasmacytoid, cuboidal, epithelioid, clear
  • ​Stroma: Product of myoepithelial cells, varies in appearance from myxoid to chondroid to chondromyxoid; may appear fibrous and/or vascular
• Variable growth patterns: tubular, solid, cystic, trabecular, cribriform, papillary, reticular, or lattice-like
• Other cell components may include:
  • Squamous cells with or without keratinization
  • Mucous cells, clear cells, sebaceous cells, oncocytic cells

Ancillary Testing:

• IHCs (variable reactivity)
  • Epithelial cells: CK+, EMA+, CEA+
  • Myoepithelial cells: CK+, p63+, p40+, Calponin+, S100+
  • PLAG1+ (nuclear) in epithelial and myoepithelial cells
    

Pitfalls:

• Cellular PA
• Epithelial dominant PA
• Myoepithelial Dominant PA

Differential Diagnosis:

• Polymorphous Adenocarcinoma
  • Infiltrative
  • Perineural invasion
  • Linear single cell, “streaming” along periphery
  • Diffuse S100+
  • p63+ p40-
  • PLAG1-
• Adenoid Cystic Carcinoma
  • Infiltrative
  • Perineural invasion
  • MYB-NFIB
  • PLAG1-
• Myoepithelioma
  • One cell population
  • No glandular differentiation
    
  • No chondromyxoid matrix
    
• ​Basal Cell Adenoma
  
  • ​Absence of chondromyxoid stroma
  • Prominent basal lamina encircle nests of cells
  • Beta-Catenin+ (nuclear)
• Carcinoma Ex-PA
  • Malignant component

 

Warthin's Tumor: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Basal Cell Adenoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Myoepithelioma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Oncocytoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Cystadenoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Lymphadenoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Canalicular Adenoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Salivary Gland Anlage Tumor: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Sclerosing Polycystic Adenosis: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Sialadenoma Papilliferum: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Inverted Ductal Papilloma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Intraductal Papilloma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Sebaceous Adenoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Sebaceous Lymphadenoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Carcinoma Ex Pleomorphic Adenoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Myoepithelial Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Epithelial-Myoepithelial Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Basal Cell Adenocarcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Secretory Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Oncocytic Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Acinic Cell Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Mucoepidermoid Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Clear Cell Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Adenoid Cystic Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Polymorphous Adenocarcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Salivary Duct Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Intraductal Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Adenocarcinoma, NOS: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Sebaceous Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Carcinosarcoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Poorly Differentiated Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Sialoblastoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Squamous Cell Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn

 

Lymphoepithelial Carcinoma: jnjnnm

Key Combined Elements for Diagnosis:

• hfhhf
• jjj
• kk

Microscopic Findings:

• kjn j
• nj

Ancillary Testing:

• nh
• jnn

Pitfalls:

• mn n
• jnj

Differential Diagnosis:

• hbh
• jnn