Adenoid cystic carcinoma

Adenoid cystic carcinoma  

  Definition  

  Adenoid cystic carcinoma is one of the common salivary gland malignancy.  Because of its distinctive histopathologic features, it was originally called a "cylindroma”.   The use of the term cylindroma should be avoided because it does not denote the malignant nature of the tumor and because the same term is used for a benign skin tumor.  

  Clinical features 

  The adenoid cystic carcinoma can occur in any salivary gland site, but it occurs most commonly in the minor salivary gland.  

  The palate is the most common site.  

  It appears as a slowly growing mass. 

  Pain is a common and important finding, and may occur early in the course of the disease (due to perineural invasion).  

  Facial nerve paralysis (if the neoplasm affects the parotid). 

  Palatal tumors often are ulcerated.  

   Histogenesis  

  Adenoid Cystic Carcinoma originate from intercalated duct cells and myoepithelial cells. 

  Histopathologic features  

  The adenoid cystic carcinoma is composed of a mixture of myoepithelial cells and ductal cells. 

  The ductal cells are small and cuboidal, with deeply basophilic nuclei and little cytoplasm. 

  Myoepithelial cells have clear cytoplasm and darkly staining angular nuclei. 

  Three histopathologic patterns are recognized: 
(1) cribriform , (2) tubular, and (3) solid.  

(1) Cribriform pattern  

  Is the most common pattern. 
  It is characterized by islands of basaloid epithelial cells that contain multiple cystic spaces resembling swiss cheese.  
  These spaces often contain basophilic mucoid material.  

(2) Tubular pattern  
  The tumor cells occur as multiple small ducts or tubules within a hyalinized stroma.  
  The duct like spaces are lined by an inner row of cuboidal epithelial cells and an outer zone of myoepithelial cells. 

(3) Solid pattern  
  It consists of large islands or sheets of cuboidal epithelial cells.  
  This type may  also show more pleomorphism and mitotic activity than the other forms. 
  This type is the most aggressive type.