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Non-Odontogenic Tumors and Jaw Dysplasias

Q: What histological variants of ameloblastoma are distinguished?

Follicular variant — the most typical variant, consisting of epithelial cell islands resembling the developing enamel organ of a tooth germ.Plexiform variant — represented by irregularly shaped epithelial cords intertwining in a network.Granular cell variant — a rare histological variant of ameloblastoma.Monocystic variant — a rare variant of ameloblastoma within a cyst wall.Acanthomatous variant — the type of ameloblastoma with the highest tendency to recur.Desmoplastic variant — one of the histological architectural variants of ameloblastoma.Squamous cell variant — one of the histological architectural variants of ameloblastoma.Basal cell variant — one of the histological architectural variants of ameloblastoma.

Tumores non odontogenici maxillarum

For medical students2 min readUpdated 2026-10-10

Neoplasms of the jaw bones comprise a broad group of lesions developing from tissue components of the maxillofacial system. Morphologically, they range from developmental malformations (hamartomas) to true tumors with locally destructive growth requiring precise histological verification.

SignAmeloblastoma produces a characteristic multilocular "soap bubble" radiolucent pattern on radiographs.

ParakeratosisCauses aggressive growth and frequent recurrences of the keratocystic odontogenic tumor.

HamartomaAn odontoma is not a true neoplasm, but rather a developmental malformation of dental tissues.

RecurrenceThe acanthomatous variant of ameloblastoma can recur even after 10 years.

Epithelial Jaw Tumors

Ameloblastoma is a classic tumor characterized by a multilocular area of bone destruction separated by thin septa. Histologically, the follicular variant is most common: the tumor consists of epithelial islands resembling a developing enamel organ. The periphery of the islands is lined by tall columnar cells, while the center contains a loose network of stellate cells (stellate reticulum). The stroma is sparse and loose. In the plexiform variant, epithelial cords intertwine in a network. Monocystic and peripheral forms have the best prognosis.

Adenomatoid odontogenic tumor is encapsulated, consisting of duct-like structures (lined by cuboidal or tall columnar epithelium) and a sparsely fibrous stroma. It is more common in young women in the upper canine region (often impacted). It does not recur after removal.

Pindborg tumor (calcifying epithelial odontogenic tumor) consists of large polygonal cells with eosinophilic cytoplasm and nuclear polymorphism. It is distinguished by locally destructive growth.

Keratocystic Odontogenic Tumor

Previously, this lesion was called a primordial or primary cyst. It accounts for up to 10% of all jaw cysts, localized predominantly in the mandible (in the third molar region) and extending along its long axis. The cyst wall is thin, fibrous, and lined by a wide layer of stratified squamous keratinizing epithelium.

Two histological types are distinguished:

Parakeratinizing type: possesses a high potential for aggressive growth and recurs more frequently.
Orthokeratinizing type (orthokeratinized form).

Mesenchymal Tumors and Cementomas

The group of mesenchymal neoplasms includes:

Odontogenic myxoma: lacks a capsule, grows destructively as a mucous mass. It consists of stellate cells, anastomosing processes, and small islands of epithelium.
Odontogenic fibroma: has a pseudocapsule and extremely rare recurrence.

"Cemental tumors" (fibro-osseous-cemental lesions) are united by the presence of cementum-like tissue. The most significant are:

Cementoblastoma (true cementoma): mineralized sheets of bone and cementum (with cementoblasts and cementoclasts), closely associated with the tooth root and causing its resorption.
Cementifying fibroma: fibrous tissue with calcified "cementicles".

Mixed Tumors and Odontomas

While an ameloblastic fibroma contains only epithelial and mesenchymal elements, an ameloblastic fibro-odontoma also contains hard dental tissues (enamel and dentin).

An odontoma is a developmental anomaly containing all dental tissues. In most cases, it is asymptomatic. Complex (complex and compound) odontomas are divided into:

Complex odontoma: a chaotic mixture of enamel and dentin, appearing on radiographs as an amorphous radiopaque mass.
Compound odontoma: consists of ordered rudimentary teeth separated by fibrous tissue, which is clearly visualized radiologically.

Malignant Lesions

Odontogenic carcinomas are extremely rare. Malignant ameloblastoma (ameloblastic carcinoma) is characterized by rapid growth and marked bone destruction. The main diagnostic criterion on microscopic examination is the presence of cellular atypia and polymorphism while preserving the follicular architecture typical of the original benign tumor.

Mnemonic

To remember complex vs compound odontomas: COmplex is COnjoined/mixed into a chaotic mass (amorphous on X-ray). COMPOUND is COMPOUNDed of separate, orderly rudimentary teeth.

Frequently asked questions

What histological variants of ameloblastoma are distinguished?

Follicular variant — the most typical variant, consisting of epithelial cell islands resembling the developing enamel organ of a tooth germ.
Plexiform variant — represented by irregularly shaped epithelial cords intertwining in a network.
Granular cell variant — a rare histological variant of ameloblastoma.
Monocystic variant — a rare variant of ameloblastoma within a cyst wall.
Acanthomatous variant — the type of ameloblastoma with the highest tendency to recur.
Desmoplastic variant — one of the histological architectural variants of ameloblastoma.
Squamous cell variant — one of the histological architectural variants of ameloblastoma.
Basal cell variant — one of the histological architectural variants of ameloblastoma.

What benign non-odontogenic jaw tumors are included in the classification?

Benign non-odontogenic tumors of various tissue origins occur in the jaw bones, analogous to tumors of other skeletal bones:

Bone-forming
Cartilage-forming
Connective tissue
Bone marrow
Vascular
Neurogenic
Smooth muscle
Giant cell tumor (osteoclastoma, osteoblastoclastoma, brown tumor) — a neoplasm that stands apart in the structure of non-odontogenic jaw tumors.

What are the characteristic microscopic features of fibrous dysplasia of the jaws?

Proliferation of cellular fibrous osteogenic tissue replacing normal mature jaw bone.
Formation of primitive bone trabeculae due to incomplete osteogenesis.
Immature bone trabeculae have irregular shapes and visually resemble "Chinese letters" (or "Chinese characters") on hematoxylin and eosin staining.

How does ameloblastic fibroma differ from ameloblastic fibro-odontoma?

Ameloblastic fibroma completely lacks hard dental tissues (enamel or dentin), whereas fibro-odontoma necessarily contains them.

What is the key histological feature of malignant ameloblastoma?

Despite pronounced signs of malignancy (cellular atypia and polymorphism), this carcinoma retains the characteristic follicular architecture of the original tissue.

What macroscopically distinguishes a jaw myxoma?

Odontogenic myxoma lacks a capsule, has indistinct borders, and grows as a yellowish-white mucous-like mass, destroying surrounding tissues.

Go deeper

Cellular composition of rare ameloblastoma variants (granular cell, monocystic)
Radiographic differences between simple and complex odontomas
Histogenesis of cementum-like tissue in periapical cemento-osseous dysplasia
Surgical management features for the acanthomatous ameloblastoma type
Differential diagnosis of keratocystic odontogenic tumor with predominant parakeratosis