Non-Odontogenic Tumors of the Jaws

Excerpt

Non-odontogenic tumor of the jaw is a term that encompasses a vast range of pathologies that cannot be fully dealt with below. Instead, the focus will be on pathology that is more commonly encountered in clinical practice, although many are still exceedingly rare. Six tumors will be covered in detail: osteosarcoma, fibrous dysplasia, central giant cell granuloma, osteoma, osteochondroma, and osteoblastoma. Below is a more thorough classification of non-odontogenic tumors of the jaw, divided by tissue of origin, highlighting the breadth of the topic.

Neoplasms of Bone

1. Benign

   1. Osteoma

   2. Osteoblastoma

   3. Osteoid osteoma

   4. Ossifying fibroma

   5. Chondroma

   6. Chondroblastoma

   7. Chondromyxoid fibroma

2. Malignant

   1. Osteosarcoma

   2. Ewing’s sarcoma

   3. Chondrosarcoma

   4. Metastases

Fibroconnective or Fibro-osseous

1. Benign

   1. Fibrous dysplasia

   2. Cherubism

   3. Non-ossifying fibroma

   4. Desmoplastic fibroma

2. Malignant

   1. Fibrosarcoma

Histocyte Derived

1. Benign

   1. Central giant cell granulomas

2. Malignant

   1. Undifferentiated pleomorphic sarcoma

Fat Derived

1. Benign

   1. Lipoma

2. Malignant

   1. Liposarcoma

Muscle Derived

1. Benign

   1. Leiomyoma

2. Malignant

   1. Leiomyosarcoma

Vascular Derived

1. Benign

   1. Central hemangioma

   2. Lymphangioma

   3. Hemangiopericytoma

2. Malignant

   1. Angiosarcoma

Nerve Derived

1. Benign

   1. Solitary neurofibroma

   2. Neurilemoma

Hematological

1. Primary lymphoma

2. Leukemia

3. Plasmacytoma and multiple myeloma

Osteosarcoma

Osteosarcoma is a malignant tumor of the bone, accounting for over half of all primary bone tumors. Osteosarcoma of the jaw accounts for 6% of all osteosarcoma,s and after squamous cell carcinomas are the second most common malignancy of the jaws. They can be defined as either primary or secondary tumors, with the latter originating from diseased bone, e.g., Paget disease, or transformation of benign tumors. They are graded and classified based on histological features.

Fibrous Dysplasia

Fibrous dysplasia is a fibro-osseous disease that causes abnormal bone maturation and remodeling. It does not cause a discrete lesion but leads to abnormal bony swellings and has therefore been included as an important form of non-odontogenic tumor. Fibrous dysplasia is a rare genetic condition caused by a sporadic, somatic mutation in the GNAS 1 gene. It commonly affects the jaws, most often occurring in the maxilla, and leads to significant deformity, asymmetry, and, if present around the orbit, blindness.

It can occur in monostotic (80 to 85%) and polyostotic forms (single vs. multiple bones, respectively). McCune-Albright syndrome is a form of polyostotic fibrous dysplasia. There are associated cutaneous changes in the form of café-au-lait spots and widespread endocrinopathies. Jaffe-Lichtenstein syndrome is another polyostotic form of fibrous dysplasia with café-au-lait spots but the absence of endocrinopathies. Another term commonly encountered is craniofacial fibrous dysplasia. This refers to a polyostotic form of fibrous dysplasia in the facial skeleton, where multiple bones are affected in continuity.

Central Giant Cell Granuloma

Central giant cell granuloma is the most common non-odontogenic tumor that affects the jaws, accounting for 7% of benign jaw tumors. They are most commonly found in the anterior portion of the mandible but can affect the maxilla. They are benign but can be locally destructive. They are of osteoclastic origin and present, therefore, as expansile lytic lesions. They are usually unifocal; in the presence of multifocal or bilateral lesions underlying diagnoses of hyperparathyroidism or cherubism should be investigated.

Osteoma

An osteoma is a benign, slow-growing proliferation of compact or cancellous bone. They most often occur in the craniofacial skeleton, primarily in the paranasal sinuses. In the jaws, they are more frequently seen in the mandible and rarely reported in the maxilla. They can be divided into three types: central, peripheral, and extraskeletal. Central osteomas derive from the endosteum, peripheral from the periosteum, and extraskeletal from the soft tissues, specifically muscles.

Gardener syndrome must be investigated as an underlying diagnosis in either the presence of multiple osteomas or osteoma in children. This is an autosomal dominant condition that leads to osteomas, fibromatosis, and polyposis of the large intestines. These adenomatous polyps ultimately undergo malignant transformation and lead to adenocarcinomas of the large intestines in all patients.

Osteochondroma

Osteochondroma is a benign hamartoma in the form of cartilage capped, bony outgrowth. They are primarily found in the axial skeleton in areas of endochondral ossification. Consequently, they are rare in the facial skeleton, as this primarily undergoes membranous ossification. When they do occur, they appear in the mandibular condyle, occasionally also occurring in the coronoid process. Their growth pattern can classify them as either exophytic or globular. Exophytic lesions tend to develop in stalk-like attachments, primarily from the condylar head. Globular lesions deform the whole of the condylar head in a lobular manner with a vertical growth plane.

Osteoblastoma

Osteoblastoma is a rare benign neoplasm; it is primarily found in the vertebral column but can occur in the jaws, most commonly the mandible. There is significant debate surrounding their natural course of progression and histology; consequently, diagnosis can be challenging. They can be divided into benign and aggressive subtypes. Aggressive tumors are locally destructive, have high recurrence rates, and can be difficult to distinguish from low-grade osteosarcoma.

Surrounding literature will often use terms such as ‘osteoid osteoma,’ ‘juvenile active ossifying fibroma,’ and ‘aggressive osteoblastoma’ to describe this pathology. Osteoid osteoma is histologically indistinguishable from osteoblastoma but will exhibit pain as a more prominent feature. Some believe it represents a different pathology entirely, and others feel it is an early phase of the developing osteoblastoma. Juvenile active ossifying fibroma and aggressive osteoblastoma both describe the same subtype of osteoblastoma. This aggressive subtype, described above, is more often seen in young adults.