Pleomorphic Adenoma of parotid gland

Benign: Pleomorphic Adenoma,

Malignant: carcinoma ex pleomorphic adenoma

Pleomorphic adenoma consists of mixed epithelial (left) and mesenchymal

cell components(right)

• This is the commonest tumor of salivary glands and commonly occurs in parotid.

• They are benign tumors derived from mixture of epithelial (ductal epithelium) and myoepithelial cells and therefore show both epithelial and mesenchymal differentiation

• It is somewhat commoner in females, presenting in fourth to sixth decades.

• Patients present with a small, firm, freely movable, painless swelling which slowly increases in size.

• Patient has complaints of difficulty in mastication, talking and breathing so is detected early.

•Being radioresistant these tumors have to be surgically resected. They have a tendency to recur after excision.

•Benign pleomorphic adenomas have 3 to 15% chances of malignant

transformation. The incidence of malignant transformation increases

with duration of tumor.•The malignant tumor is called as carcinoma ex pleomorphic adenoma. They are highly aggressive and show high mortality rates.

GROSS APPEARANCE• The tumor is well circumscribed

psuedoencapsulated, rounded multilobulated, firm mass rarely exceeding 6cm in greatest dimension.

• Although they are encapsulated at some locations the capsule is not fully developed (psuedoencapsulated) giving protrusions in surrounding gland rendering enucleation hazardous.

• The cut surface is gray white with myxoid and blue translucent areas of chondroid.

Histopathology• The diverse histologic pattern is in

fact the characteristic feature of this neoplasm.

• Inside fibrous capsule some areas have cuboidal cells arranged in tubes or ductlike structures or strands or sheets of cells.

• These elements are typically dispersed in a mesenchyme like background of loose myxoid connective tissue stroma containing islands of chondroid tissue .

• Sometimes well developed ducts lined by cuboidal to columnar cells with an underlying layer of deeply chromatic small myoepithelial cells are seen.

• Loose myxoid tissue is predominant feature while foci of hyalinised connective tissue or cartilage like material and even bone may occur.

• Islands of well differentiated squamous epithelium may also occur.

• Sometimes tumor cells assume a stellate, polyhedral or spindle form.

• In most cases there is no epithelial dysplasia or mitotic activity.

Epithelial elements

Myxoid tissue

Biphasic appearance resulting from the admixture of epithelium & stroma.

(20X)】 Epithelial component.　

epithelium

stromamyxoid

(20X)】 Epithelial component.

Epithelial proliferation

(40X)】 Glandular (ductal) component.

DUCT

Epithelium

stroma