Pleomorphic Adenoma Benign Mixed Tumor

the most common salivary neoplasm parotid tumors>minor gland tumors Although the basic tumor pattern is highly variable, rarely are the individual cells actually pleomorphic

derived from a mixture of ductal and myoepithelial elements

Clinical and Radiographic Features a painless, slowly growing, firm mass at any age but is most 30-50. slight female predilection.

The palate is the most common site for minor gland mixed tumors (60% of intraoral examples) >upper lip (20%) > buccal mucosa (10%). Palatal tumors almost always are found on the posterior lateral aspect of the palate smooth-surfaced, dome-shaped masses Palatal tumors are not movable

Histopathologic Features

typically a well-circumscribed, encapsulated tumor A well-defined tumor has a thin fibrous capsule lack of complete encapsulation is more common for minor gland tumors

The tumor is composed of a mixture of ductal epithelium and myoepithelial cells within a mesenchyme-like background that is highly variable ducts cystic structures islands or sheets of cells Cords of ductal epithelium Keratinizing squamous cells mucus-producing cells epithelium often forms

Myoepithelial cells with a variable morphology The highly characteristic "stromal" changes angular Spindled plasmacytoid ( resembling plasma cells ) (more prominent in tumors arising in the minor glands) cells are rounded and demonstrate an eccentric nucleus and eosinophilic hyalinized cytoplasm

Stromal changes Myxomatous background chondroid appearance hyalinized change Fat or osteoid (rarely)

Myxomatous background Extensive accumulation of mucoid material between the tumor cells

chondroid appearance or chondroid metaplasia (Vacuolar degeneration of cells in these areas)

Cartilage may sometimes be present in the stroma.

Many of the ducts and myoepithelial cells are surrounded by a hyalinized, eosinophilic background alteration

A "classic" appearance with ductal elements in a myxoid stroma The tubules is composed of two layers of cells

Cords of ductal epithelium in a loose myxomatous stroma.