Recurrence rate of solid form of tumour is lower than classic form.

Currently, the genetic or environmental factors that predispose an individual for chondroblastoma are not well known or understood. Chondroblastoma affects males more often than females at a ratio of 2:1 in most clinical reports. Furthermore, it is most often observed in young patients that are skeletally immature, with most cases diagnosed in the second decade of life. Approximately 92% of patients presenting with chondroblastoma are younger than 30 years. There is no indication of a racial predilection for chondroblastoma.

Although not specific to one mode of management, lesion size, patient sex, or follow-up, the recurrence rate for chondroblastoma is relatively high, and has been shown in select studies to be dependent upon the anatomical location, method of treatment, and biological aggressiveness of the initial lesion. The rate of recurrence is highly variable, ranging between 5% and 40%, as study results are generally inconclusive. However, local recurrence for long bone lesions is around 10%, with chondroblastoma in flat bones having higher recurrence and more complications. Recurrences are more common in cases involving an open epiphyseal plate where they can be attributed to inadequate curettage to avoid damage. Lesions of the proximal femur are particularly problematic because of difficulties accessing the femoral head for complete excision. Chondroblastoma may recur in the soft tissue surrounding the initial lesion, especially in the case of incomplete curettage. Recurrences have been shown to occur between 5 months and 7 years after initial treatment and are generally treated with repeat curettage and excision of affected soft-tissue. No histological differences have been seen between recurrent and non-recurrent chondroblastomas.

Rarely, more aggressive chondroblastomas can metastasize. The most common location for metastases is the lung, with some cases also involving secondary bone sites, soft tissue, skin, or the liver. The prevalence of metastatic chondroblastoma, however, is quite low and is believed to be less than 1%. There is no relationship established between metastasis and previous surgery, non-surgical treatment, anatomical location, or patient age. Survival of patients with metastatic lesions is better when the metastases are surgically resectable, as chemotherapy has been shown to have little to no benefit. Prognosis is bleak for patients with malignant chondroblastomas that are resistant to surgery, radiation, and chemotherapy. However, patients with resectable metastases have survived for several years following diagnosis.

While recurrence is the most common complication of chondroblastoma other issues include post-surgery infection, degenerative joint disease, pathological fractures, failure of bone grafts, pre-mature epiphyseal closure, functional impairment, and malignant transformation. Complications are less common in patients presenting with chondroblastoma in accessible areas. Overall, patients with more classical chondroblastoma (appearing in long bones, typical presentation) have better prognoses than patients with atypical chondroblastoma (flat bones, skull, etc.).

It is common in age group of 10–30 years. It is second most common tumor of spine and commonest benign tumor of pelvis in pediatric population. Incidence is slightly more in males than females (1.3:1).

In the US, Osteoblastomas account for only 0.5-2% of all primary bone tumors and only 14% of benign bone tumors making it a relatively rare form of bone tumor.

In regards to morbidity and mortality, conventional osteoblastoma is a benign lesion with little associated morbidity. However, the tumor may be painful, and spinal lesions may be associated with scoliosis and neurologic manifestations. Metastases and even death have been reported with the controversial aggressive variant, which can behave in a fashion similar to that of osteosarcoma. This variant is also more likely to recur after surgery than is conventional osteoblastoma.

Osteoblastoma affects more males than it does females, with a ratio of 2-3:1 respectively. Osteoblastoma can occur in persons of any age, although the tumors predominantly affect the younger population (around 80% of these tumors occurs in persons under the age of 30). No racial predilection is recognized.

It usually presents in the vertebral column or long bones. Approximately 40% of all osteoblastomas are located in the spine. The tumors usually involve the posterior elements, and 17% of spinal osteoblastomas are found in the sacrum. The long tubular bones are another common site of involvement, with a lower extremity preponderance. Osteoblastoma of the long tubular bones is often diaphyseal, and fewer are located in the metaphysis. Epiphyseal involvement is extremely rare. Although other sites are rarely affected, several bones in the abdomen and extremities have been reported as sites of osteoblastoma tumors.

Age and gender have an effect on the incidence of these lesions; they are more prevalent in women than men (though still common in both genders), and they appear more frequently with age. Due to the standard of medical care and screening in developed countries, it is increasingly rare for primary hyperparathyroidism to present with accompanying bone disease. This is not the case in less developed nations, however, and the two conditions are more often seen together.

The cause of osteoblastoma is unknown. Histologically, osteoblastomas are similar to osteoid osteomas, producing both osteoid and primitive woven bone amidst fibrovascular connective tissue, the difference being that osteoblastoma can grow larger than 2.0 cm in diameter while osteoid osteomas cannot. Although the tumor is usually considered benign, a controversial aggressive variant has been described in the literature, with histologic features similar to those of malignant tumors such as an osteosarcoma.

The majority of cases occur in the second and third decades, with approximately 75% of cases occurring before the age of 30 years 1,12-15. There is no recognised gender predilection. Examples have however been seen in patients up to the age of 75 years. In some series there is a male predilection 12 whilst in others no such distribution is found 2

Chondromyxoid fibroma is a type of cartilaginous tumor.

Most cases are characterised by GRM1 gene fusion or promoter swapping. It can be associated with a translocation at t(1;5)(p13;p13).

A chondromyxoid fibroma (CMF) is an extremely rare benign cartilaginous neoplasm which accounts for < 1% bone tumours.

Treatment consists of wide resection or amputation. Metastases are rare at presentation but may occur in up to 30% of patients during the disease course. Prognosis is excellent, with overall survival of 85% at 10 years, but is lower when wide surgical margins cannot be obtained. This tumor is insensitive to radiation so chemotherapy is not typically used unless the cancer has metastasized to the lungs or other organs.

An osteoma (plural: "osteomata") is a new piece of bone usually growing on another piece of bone, typically the skull. It is a benign tumor.

When the bone tumor grows on other bone it is known as "homoplastic osteoma"; when it grows on other tissue it is called "heteroplastic osteoma".

Osteoma represents the most common benign neoplasm of the nose and paranasal sinuses. The cause of osteomata is uncertain, but commonly accepted theories propose embryologic, traumatic, or infectious causes. Osteomata are also found in Gardner's syndrome. Larger craniofacial osteomata may cause facial pain, headache, and infection due to obstructed nasofrontal ducts. Often, craniofacial osteoma presents itself through ocular signs and symptoms (such as proptosis).

A nonossifying fibroma (also called fibroxanthoma) is a common benign bone tumor in children and adolescents. However, it is controversial whether it represents a true neoplasm or rather a developmental disorder of growing bone. Radiographically, the tumor presents as a well marginated radiolucent lesion, with a distinct multilocular appearance. These foci consist of collagen rich connective tissue, fibroblasts, histiocytes and osteoclasts. They originate from the growth plate, and are located in adjacent parts of the metaphysis and diaphysis of long bones, most often of the legs. No treatment is needed in asymptomatic patients and spontaneous remission with replacement by bone tissue is to be expected.

Multiple nonossifying fibromas occur in Jaffe-Campanacci syndrome in combination with cafe-au-lait spots, mental retardation, hypogonadism, ocular and cardiovascular abnormalities.

The brown tumor is a bone lesion that arises in settings of excess osteoclast activity, such as hyperparathyroidism. It is not a true neoplasm, as the term "tumor" suggests; however, it may mimic a true neoplasm. It most commonly affects the maxilla and mandible, though any bone may be affected. Brown tumours are radiolucent on x-ray.

Adamantinoma (from the Greek word "adamantinos", meaning "very hard") is a rare bone cancer, making up less than 1% of all bone cancers. It almost always occurs in the bones of the lower leg and involves both epithelial and osteofibrous tissue.

The condition was first described by Fischer in 1913.

The tumor is rare, affecting adults in the 4th decade most commonly. Patients are usually younger than those who present with a lipoma. There is a slight male predominance. Hibernoma are most commonly identified in the subcutaneous and muscle tissue of the head and neck region (shoulders, neck, scapular), followed by thigh, back, chest, abdomen, and arms. In rare cases hibernoma may arise in bone tissue, however it is an incidental finding.

Recurrence is common, although the recurrence rates for block resection followed by bone graft are lower than those of enucleation and curettage. Follicular variants appear to recur more than plexiform variants. Unicystic tumors recur less frequently than "non-unicystic" tumors. Persistent follow-up examination is essential for managing ameloblastoma. Follow up should occur at regular intervals for at least 10 years. Follow up is important, because 50% of all recurrences occur within 5 years postoperatively. Recurrence within a bone graft (following resection of the original tumor) does occur, but is less common. Seeding to the bone graft is suspected as a cause of recurrence. The recurrences in these cases seem to stem from the soft tissues, especially the adjacent periosteum. Recurrence has been reported to occur as many as 36 years after treatment.

To reduce the likelihood of recurrence within grafted bone, meticulous surgery with attention to the adjacent soft tissues is required.

To date, the specific cause of Gorham's disease remains unknown.

Bone mass and strength are obtained and maintained through a process of bone destruction and replacement that occurs at the cellular level throughout a person's life. Cells called osteoclasts secrete enzymes that dissolve old bone, allowing another type of cells called osteoblasts to form new bone. Except in growing bone, the rate of breakdown equals the rate of building, thereby maintaining bone mass. In Gorham's disease that process is disrupted.

Gorham and Stout found that vascular anomalies always occupied space that normally would be filled with new bone and speculated that the presence of angiomatosis may lead to chemical changes in the bone. Gorham and others speculated that such a change in the bone chemistry might cause an imbalance in the rate of osteoclast activity to osteoblast activity such that more bone is dissolved than is replaced. Beginning in the 1990s there were reports of elevated levels of a protein called interleukin-6 (IL-6) being detected in patients with the disease, leading some to suggest that increased levels of IL-6 and vascular endothelial growth factor (VEGF) may contribute to the chemical changes Gorham and others believed were the cause of this type of osteolysis.

In 1999 Möller and colleagues concluded, "The Gorham-Stout syndrome may be, essentially, a monocentric bone disease with a focally increased bone resorption due to an increased number of paracrine – or autocrine – stimulated hyperactive osteoclasts. The resorbed bone is replaced by a markedly vascularized fibrous tissue. The apparent contradiction concerning the presence or absence or the number of osteoclasts, may be explained by the different phases of the syndrome." They further stated that their histopathological study provided good evidence that osteolytic changes seen in Gorham's disease are the result of hyperactive osteoclastic bone. However, others have concluded that lymphangiomatosis and Gorham's disease should be considered as a spectrum of disease rather than separate diseases.

While there is consensus that Gorham's is caused by deranged osteoclastic activity, there is not yet conclusive evidence as to what causes this deranged behavior to begin.

The annual incidence rates per million for ameloblastomas are 1.96, 1.20, 0.18 and 0.44 for black males, black females, white males and white females respectively. Ameloblastomas account for about one percent of all oral tumors and about 18% of odontogenic tumors. Men and women tend to be equally affected, although women tend to be 4 years younger than men when tumors first occur and tumors appear to be larger in females.

Gorham's disease (pronounced GOR-amz), also known as Gorham vanishing bone disease and phantom bone disease, is a very rare skeletal condition of unknown cause, characterized by the uncontrolled proliferation of distended, thin-walled vascular or lymphatic channels within bone, which leads to resorption and replacement of bone with angiomas and/or fibrosis. Current treatments are experimental only.

A connective tissue neoplasm or connective tissue tumor is a neoplasm arising from the tissues of the connective tissue. (Not all tumors "in" the connective tissue are "of" the connective tissue.)

Metastatic carcinoma is able to grow at sites distant from the primary site of origin; thus, dissemination to the skin may occur with any malignant neoplasm, and these infiltrates may result from direct invasion of the skin from underlying tumors, may extend by lymphatic or hematogenous spread, or may be introduced by therapeutic procedures.

The most common malignancy found in bone is metastatic carcinoma.

An odontogenic keratocyst is a rare and benign but locally aggressive developmental cyst. It most often affects the posterior mandible. It most commonly presents in the third decade of life.

In the WHO/IARC classification of head and neck pathology, this clinical entity had been known for years as the odontogenic keratocyst; it was reclassified as keratocystic odontogenic tumour (KCOT) from 2005 to 2017. In 2017 it reverted to the earlier name, as the new WHO/IARC classification reclassified OKC back into the cystic category. The WHO/IARC classification no longer considers it a neoplasm, because the evidence supporting that hypothesis (for example, clonality) is considered insufficient. However, this is an area of hot debate within the head and neck pathology community, and some pathologists still regard OKC as a neoplasm despite the reclassification.

This is a very rare tumor, since only about 1 in 35,000 to 40,000 people have VHL, of whom about 10% have endolymphatic sac tumors. Patients usually present in the 4th to 5th decades without an gender predilection. The tumor involves the endolymphatic sac, a portion of the intraosseous inner ear of the posterior petrous bone.

Vascular tissue neoplasms, like neoplasms of all tissues, are classified to benign and malignant ones, according to their biological behavior.

Most malignant vascular tumors are considered sarcomas, a major histological group of tumors, arising from transformed cells of mesenchymal origin.

- Hemangiosarcoma

- Hemangiopericytoma

- Kaposi's Sarcoma

- Hemangioblastoma

- Lymphangiosarcoma