C

Fig. 1.69 Giant cell tumour. A Clustering of multinucleated giant cells. On the right are remnants of Rathke's pouch with ciliated columnar epithelium. B Densely packed giant cells with up to 20 nuclei. Intermingled are macrophages and oval stromal cells.

Fig. 1.69 Giant cell tumour. A Clustering of multinucleated giant cells. On the right are remnants of Rathke's pouch with ciliated columnar epithelium. B Densely packed giant cells with up to 20 nuclei. Intermingled are macrophages and oval stromal cells.

found in the mononuclear cells, but atypical ones do not occur and, if present, are a strong indicator for progression to malignant GCT {272}. Intravascular growth, particularly in the tumour periphery, may be noted, but has no prognostic relevance {207,775,2831}.

Histogenesis

The ovoid to plump spindled stromal cells represent the active proliferating tumour cell pool {2190}, capable of secreting cytokines and differentiation factors, including receptor activator of nuclear factor k ligand (RANKL) {2207}. These factors attract monocytes, the second cell type in GCT, and promote fusion to osteoclasts, the third cell type in GCT. The monocytes and osteoclast-like giant cells represent a non-neoplastic tumour component {775,2831}.

Genetics

Cytogenetic studies reveal telomeric associations (TAS) as the most frequent chromosomal aberration {272}. Some GCTs show rearrangements in 16q22 or 17p13, similar to aneurysmal bone cyst, which is often associated with GCT. These rearrangements may indicate the possible presence of an aneurysmal bone cyst component {775}.

Prognosis and predictive factors

GCT of the skull is a locally aggressive lesion. Treatment consists of complete removal, if possible. Radiotherapy is also applied {207,1146}. Histologically malignant GCT of the skull has been rarely described, sometimes associated with Paget disease {365,1474}.

Chondroma

Chondromas of the sinonasal tract are extremely rare, and any cartilaginous tumour greater than 2 cm occurring in this site should be considered potentially malignant until proven otherwise.

ICD-O code

Osteoma

9220/0

Definition

A benign lesion composed of mature bone with a predominantly lamellar structure.

ICD-O code

9180/0

Synonyms

In the jaws and calvaria, the terms exos-tosis and osteoma have been used interchangeably {131}. The term 'osteoma' should be used in a restricted sense limited to lesions of the paranasal sinuses, facial bones and orbit, although it has been used in the literature to describe calvarian and mandibular ivory exosto-sis, surface (juxtacortical) osteoma of the long bones, torus palatinus and torus mandibularis.

Epidemiology

Among patients with sinonasal radiographs taken for a variety of reasons, up to 1% have been found to have osteo-mas. It may occur at any age, but especially in young adults. There is a 2:1 male predominance.

Localization

The osteomas may be single or multiple; central or on the bone surface, where they can be sessile or rarely pedunculat-ed. They occur most commonly in the frontal and ethmoid sinuses. The maxillary and sphenoid sinuses are infrequently involved. In the jaws, the angle of the mandible is more frequently involved than the coronoid process or condyle.

Clinical features

Osteomas are often asymptomatic and incidentally discovered. However they can produce pain or symptoms related to the location. Multiple jaw osteomas are a frequent component of the Gardner syndrome (a form of familial adenomatous polyposis), being found in 70-90% of patients.

Osteomas are radiodense, sharply defined, well-circumscribed lesions occurring in either a central or peripheral location.

Macroscopy

The lesion is a well-circumscribed white bony mass, which is occasionally polypoid or exophytic.

Histopathology

Osteoma is characterised by compact cortical bone with scanty intervening fibrovascular stroma. In some cases, there is a peripheral rim of dense sclerotic lamellar bone surrounding trabeculae of lamellar or occasionally woven bone separated by fibrofatty vascular tissue.

Genetic predisposition

The presence of multiple osteomas is an important clue that the patient may have Gardner syndrome.

Prognosis and predictive factors

No therapy is required unless the lesion causes cosmetic or functional problems. A local resection is the treatment of choice in such circumstances.

Chondroblastoma and chondromyxoid fibroma

ICD-O codes

Chondroblastoma 9230/0

Chondromyxoid fibroma 9241/0

Chondroblastomas and chondromyxoid fibromas are rare in the head and neck {177,988,1024,1 120,1185,1348,1349, 1356,1466,2559,2683,2730}. See WHO Classification of Tumours of Soft Tissue and Bone {775}.

tumours occurring outside the head and neck. Females are more commonly affected than males.

Localization

More than half of the lesions occur in the coronoid process of the mandible. The condyle can also be involved.

Clinical features

Osteochondroma involving the coronoid process or the condyle causes difficulty in opening the mouth or dysfunction of the temporomandibular joint. On plain radiographs, flaring of the cortex in continuity with the underlying bone and varying degrees of calcification and/or ossification are present. The cartilaginous cap is of variable thickness.

Macroscopy

A cartilaginous cap covers the bony protrusion.

by salicylates. It is very rare in the head and neck. It occurs in young patients (first three decades), with male predominance. On plain radiographs, dense cortical sclerosis surrounds a radiolucent nidus. Histologically, the nidus shows interconnected, ossified woven bone rimmed by osteoblasts. Fibrous tissue, vessels and multinucleated giant cells are identified in between the bony tra-beculae. See WHO Classification of Tumours of Soft Tissue and Bone {775}.

Osteoblastoma

ICD-O code

9200/0

Definition

A rare, benign, bone-forming tumour in which osteoblasts rim woven bony tra-beculae, forming a mass usually over 2 cm.

Osteochondroma (exostosis)

Definition

A pedunculated or sessile exophytic bony projection with a cartilaginous cap. The bony component is continuous with the underlying bone.

ICD-O code

9210/0

Epidemiology

Osteochondroma is one of the most common lesions of the long and flat bones. It may be solitary or multiple. In the facial bones, osteochondromas are very rare and almost invariably single. Osteochondromas of the facial skeleton have not been reported in the setting of multiple hereditary exostoses. The mean age at diagnosis is 40 years, which is older than that of patients with

Histopathology

The cap consists of hyaline cartilage, and the osteochondral junction resembles the growth plate. A well-defined zone of enchondral ossification matures into cancellous bone with marrow.

Prognosis and predictive factors

Excision is curative. No recurrence or malignant transformation has been reported in osteochondromas of the jaws.

Osteoid osteoma

ICD-O code

9191/0

Osteoid osteoma is a benign bone-forming tumour of limited growth potential, usually less than 1.5 cm, typically associated with nocturnal pain that is relieved

Epidemiology

Osteoblastoma is rare, and 90% of cases occur below the age of 30 years. It is more common in males.

Localization

In the head and neck, the most common site of involvement is the jaws, followed by the cervical vertebrae and the skull {1570}. The mandible is affected about two to three times more often than the maxilla. Most arise in the body of the mandible, rarely in the midline or coro-noid process.

Clinical features

Osteoblastomas of the jaw cause swelling and toothache, and in the cervical spine, pain, scoliosis and nerve root compression. In contrast to osteoid osteoma, the pain is rarely nocturnal and not relieved by salicylates.

Fig. 1.70 A Osteoma of the right parietal bone. Mature lamellar bone with osteon-like structures. B Osteoid osteoma. Osteoblasts surround the trabeculae. C Nidus of an osteoblastoma, showing a single layer of osteoblasts lining the bony trabeculae.

Fig. 1.70 A Osteoma of the right parietal bone. Mature lamellar bone with osteon-like structures. B Osteoid osteoma. Osteoblasts surround the trabeculae. C Nidus of an osteoblastoma, showing a single layer of osteoblasts lining the bony trabeculae.

Fig. 1.71 Nasal chondromesenchymal hamartoma. A Multiple tumour fragments with a mucosal surface and nodules of cartilage. B Cartilaginous nodule, surrounded by cellular stroma.

On plain radiographs, osteoblastoma is a sharply circumscribed, oval-round lytic lesion. It may have a mixed lytic and sclerotic pattern, reflecting the degree of mineralization of the matrix. A reactive bony shell is detected at the periphery. Radiographic features indistinguishable from malignant lesions are reported in about one-third of cases.

Macroscopy

It is a red and gritty lesion often with cyst formation. The border between the tumour and the host bone is very sharp.

Histopathology

Woven bony trabeculae, rimmed by osteoblasts are haphazardly distributed within a richly vascularized fibrous stro-ma accompanied by osteoclast-like giant cells. Mitotic figures may be present, but without atypical forms. Degenerative nuclear atypia is occasionally present. When large plump osteoblasts with prominent nucleoli predominate, the tumour is often referred to as epithelioid osteoblastoma or aggressive osteoblas-toma. However, these histologic features are not necessarily indicative of aggressive behaviour. Rarely, focal areas of hyaline cartilage may be identified, as well as secondary aneurysmal bone cyst-like changes. At the periphery, there is no permeative growth pattern. The histolog-ic features are identical to cementoblas-toma. Tumours showing direct continuity with the root of a tooth are preferably termed a cementoblastoma.

Prognosis and predictive factors

Curettage or local excision is the treatment of choice. In the few cases with recurrence, a further conservative treatment will control the disease.

Ameloblastoma

Ameloblastomas are very rare in the sinonasal tract and nasopharynx {1554, 2257}. See Chapter 6 on odontogenic tumours for details.

ICD-O code

9310/0

Nasal chondromesenchymal hamartoma

Definition

A tumefactive process arising in the nasal cavity and/or paranasal sinuses whose mixed chondroid, stromal, and cystic features are morphologically similar to the chest wall hamartoma.

Epidemiology

There are only 12 reported cases {45,1140,1284,1311,1678}. A pleuropul-monary blastoma was diagnosed in one of these children {1678}. One infant with the prenatal detection of hydrocephalus also had absence of the corpus callosum and hypoplasia of the cerebellar vermis. The age range is newborn to 16 years with most cases presenting in the first year of life, often before 3 months of age. There is a male predilection of approximately 3:1.

Clinical features

Signs and symptoms

Respiratory difficulty, the discovery of an intranasal mass and/or facial swelling are the most common presenting features. The respiratory distress is detected in the immediate neonatal period or develops later during feedings with accompanying cyanosis. A unilateral mass in the nasal cavity is the most consistent finding on physical examination.

Imaging

A mass density in the nasal cavity and/or the contiguous paranasal sinuses is noted on radiographic examination. Magnetic resonance or computed tomo-graphic imaging discloses a dense mass with or without calcifications or a heterogeneous signal in a lesion with cystic features. Extension or involvement of the maxillary and/or ethmoid sinuses and erosion into the anterior cranial fossa are other accompanying changes.

Macroscopy

Multiple solid and cystic fragments of tis-

Fig. 1.72 Ameloblastoma. A An intact respiratory surface is subtended by a complex ameloblastic neoplasm with many lobules displaying a central stellate retic-ulum surrounded by the palisaded columnar ameloblastic epithelium. B Reverse polarity of the hyperchromatic columnar nuclei away from the basement membrane and towards the stellate reticulum. C Granular cell ameloblastoma showing islands of granular cells.

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