'''Chondroblastoma''' is a rare, [[Benign tumor|benign]], locally aggressive bone tumor that typically affects the [[Epiphysis|epiphyses]] or [[Tubercle (anatomy)|apophyses]] of [[long bone]]s.<ref name="De" /><ref name="Romeo" /> It is thought to arise from an outgrowth of immature [[cartilage]] cells ([[chondroblast]]s) from [[secondary ossification center]]s, originating from the [[epiphyseal plate]] or some remnant of it.<ref name="Romeo" /><ref name="Ramappa" />
== Chondroblastoma ==
[[File:Chondroblastoma_-_very_high_mag.jpg|left|thumb|Micrograph of a chondroblastoma, showing characteristic features.]]
Chondroblastoma is very uncommon, accounting for only 1-2% of all [[bone tumor]]s.<ref name="De" /><ref name="Ramappa" /> It affects mostly children and young adults with most patients being in the second decade of life, or less than 20 years of age.<ref name="De" /><ref name="Kurt" /> Chondroblastoma shows a predilection towards the male sex, with a ratio of male to female patients of 2:1.<ref name="De" /><ref name="Kurt" /><ref name="Damron" /> The most commonly affected site is the [[femur]], followed by the [[humerus]] and [[tibia]].<ref name="De" /><ref name="Ramappa" /><ref name="Kurt" /><ref name="Turcotte" /> Less commonly affected sites include the [[Talus bone|talus]] and [[calcaneus]] of the [[foot]] and [[flat bone]]s.<ref name="De" /><ref name="Turcotte" />
'''Chondroblastoma''' is a rare [[benign tumor]] that originates from the [[cartilage]]-producing cells known as [[chondroblasts]]. It typically occurs in the [[epiphysis]] of long bones, most commonly affecting the [[femur]], [[tibia]], and [[humerus]]. Chondroblastoma is most frequently diagnosed in [[adolescents]] and young adults, with a higher prevalence in males.
== Pathophysiology ==
==Signs and Symptoms==
Chondroblastoma arises from the [[chondroblasts]] in the [[epiphyseal plate]] of bones. These tumors are characterized by the production of immature cartilage and are composed of chondroblasts, [[multinucleated giant cells]], and a chondroid matrix. The [[histology]] of chondroblastoma shows a distinctive "chicken-wire" calcification pattern.
The most common symptom is mild to severe pain that is gradually progressive in the affected region and may be initially attributed to a minor injury or [[Sports injury|sports-related injury]].<ref name="De" /><ref name="Ramappa" /><ref name="Damron" /><ref name="Turcotte" /> Pain may be present for several weeks, months, or years.<ref name="De" /><ref name="Damron" /> Other symptoms in order of most common to least commonly observed include [[Swelling (medical)|swelling]], a [[limp]] (when affected bone is in the lower extremity), [[joint stiffness]], and a soft tissue mass.<ref name="De" /><ref name="Turcotte" />
== Clinical Presentation ==
Patients with chondroblastoma typically present with localized [[pain]] and [[swelling]] in the affected area. The pain is often progressive and may be associated with [[joint effusion]] and [[limited range of motion]]. In some cases, the tumor may cause [[pathological fractures]].
Physical findings include localized tenderness and a decreased range of motion in the involved bone and nearby [[joint]], [[muscle atrophy]], a palpable mass, soft tissue swelling, and [[joint effusion]] in the affected area.<ref name="De" /><ref name="Damron" /><ref name="Turcotte" /> Less commonly, [[Pathologic fracture|pathological fractures]] can be found, especially in cases involving the foot.<ref name="De" /> In cases involving the [[temporal bone]], [[tinnitus]], [[dizziness]], and [[hearing loss]] have been reported.<ref name="Turcotte" />
In a publication by Turcotte et al. it was found that the average duration of symptoms for patients with chondroblastoma was about 20 months, ranging from 5 weeks to 16 years.<ref name="Damron" /><ref name="Turcotte" />
==Risk Factors==
Currently, the genetic or environmental factors that predispose an individual for chondroblastoma are not well known or understood.<ref name="De" /> Chondroblastoma affects males more often than females at a ratio of 2:1 in most clinical reports.<ref name="De" /><ref name="Ramappa" /><ref name="Kurt" /><ref name="Damron" /><ref name="Turcotte" /> Furthermore, it is most often observed in young patients that are skeletally immature, with most cases diagnosed in the second decade of life.<ref name="Romeo" /><ref name="Damron" /> Approximately 92% of patients presenting with chondroblastoma are younger than 30 years.<ref name="Damron" /> There is no indication of a racial predilection for chondroblastoma.<ref name="Damron" />
==Pathogenesis==
The etiology of chondroblastoma is uncertain, as there is no specific characteristic abnormality or [[Chromosome|chromosomal]] breaking point observed, despite [[Cytogenetics|cytogenetic]] abnormalities being highly specific for some tumors.<ref name="De" /><ref name="Damron" />
Romeo ''et al'' has noted that chondroblastoma arising in long bones mainly affects the epiphyses, while in other locations it is close to [[ossification center]]s.<ref name="Romeo" /> Additionally, rare prevalence of chondroblastoma in [[Ossification|intra-membranous ossification]] suggests a close relationship with growth plate cartilage.<ref name="Romeo" /> In chondroblastoma, growth signaling molecules may be present due to the pre-pubertal signaling network as well as cartilage growth.<ref name="Romeo" /> [[Sex steroid|Sex hormones]] are thought to be linked to this process because of the spatial relationship of chondroblastoma with the growth plate and its typical occurrence before growth plate fusion.<ref name="Romeo" /> Both [[IHH (protein)|Indian Hedgehog]]/[[Parathyroid hormone-related protein|Parathyroid Hormone-related Protein]] (IHh/PtHrP) and [[fibroblast growth factor]] (FGF) signaling pathways, important for development of the epiphyseal growth plate, are active in chondroblastoma leading to greater [[Cell proliferation|proliferation]] among the cells in the proliferating/pre-hypertrophic zone (cellular-rich area) versus the hypertrophic/calcifying zone (matrix-rich area).<ref name="De" /><ref name="Romeo" /> These findings suggest that chondroblastoma is derived from a [[mesenchymal cell]] undergoing [[chondrogenesis]] via active growth-plate signaling pathways (see [[Endochondral ossification]]).<ref name="De" /><ref name="Romeo" />
The highly heterogeneous nature of the tumor makes classification particularly difficult especially considering the origins of chondroblastoma.<ref name="Romeo" /> There are two opposing views on the nature of chondroblastoma, one favoring an [[Bone|osseous]] origin and the other favoring a [[Cartilaginous joint|cartilaginous]] origin. The work of Aigner ''et al'' suggests that chondroblastoma should be reclassified as a bone-forming neoplasm versus a cartilaginous neoplasm due to the presence of [[Osteoid|osteoid matrix]], [[type I collagen]], and absence of true cartilage matrix (collagen II).<ref name="Romeo" /><ref name="Damron" /> However, Edel ''et al'' found that [[Type II collagen|collagen II]], a marker for mature [[chondrocyte]]s, was expressed in chondroblastoma, supporting the chondroid nature of the [[neoplasm]].<ref name="Romeo" /> The results of Romeo and colleagues favor the view of Edel ''et al'' of chondroblastoma being cartilaginous in nature but recognize that any definitive determinations regarding the origin of this neoplasm are not possible because of the [[Neuroplasticity|plasticity]] of mesenchymal cells when set into different microenvironments and static approaches used in literature.<ref name="Romeo" /> Romeo ''et al'' have observed chondroblastoma neoplasms to be composed of mesenchymal cells that have completed normal chondrogenesis along with the production of osteoid and collagen I that could be the result of [[transdifferentiation]] of chondrocytes towards [[osteoblast]]s.<ref name="Romeo" />
== Diagnosis ==
== Diagnosis ==
The diagnosis of chondroblastoma is primarily based on [[imaging studies]] and [[biopsy]]. [[X-rays]] typically show a well-defined, lytic lesion in the epiphysis of the affected bone. [[Magnetic resonance imaging]] (MRI) and [[computed tomography]] (CT) scans can provide further details about the extent of the tumor and its relationship with surrounding structures. A [[biopsy]] is essential to confirm the diagnosis and differentiate it from other bone lesions.
=== Imaging Studies ===
A variety of imaging studies can be used to diagnose chondroblastoma, with [[radiographs]] being the most common.<ref name="De" /><ref name="Damron" /> Laboratory studies are not considered useful.<ref name="Damron" /> Classical chondroblastoma (appearing on long bones) appears as a well-defined eccentric oval or round lytic lesion that usually involves the adjacent [[Cortical bone|bone cortex]] without [[Periosteal reaction|periosteal]] reaction.<ref name="De" /><ref name="Turcotte" /> A [[Sclerosis (medicine)|sclerotic]] margin can be seen in some cases.<ref name="De" /><ref name="Turcotte" /> For long bone chondroblastomas the tumor is typically contained to the epiphysis or apophysis but may extend through the epiphyseal plate.<ref name="De" /><ref name="Turcotte" /> Chondroblastomas are usually located in the [[Medullary cavity|medullary]] portion of bones and can, in some cases, include the [[metaphysis]].<ref name="De" /><ref name="Turcotte" /> However, true metaphyseal chondroblastomas are rare and are typically the result of an extension from a neighboring epiphyseal legion.<ref name="De" /><ref name="Turcotte" /> Most lesions are less than 4 cm.<ref name="De" /> A mottled appearance on the radiograph is not atypical and indicates areas of [[calcification]] which is commonly associated with skeletally immature patients.<ref name="De" /> Additionally, one-third of all cases involve [[aneurysmal bone cyst]]s which are thought to be the result of stress, [[Traumatic event (physical)|trauma]] or [[Bleeding|hemorrhage]].<ref name="De" /> In cases involving older patients or flat bones, typical radiographic presentation is not as common and may mimic aggressive processes.<ref name="De" /><ref name="Turcotte" />
Other imaging techniques involve [[CT scan|computed tomography]] (CT), [[magnetic resonance imaging]] (MRI), and [[Bone scintigraphy|bone scans]], which may be helpful in determining the anatomical boundaries, associated [[edema]], or biological activity of the chondroblastoma, respectively.<ref name="De" /><ref name="Damron" />
=== Histological Findings ===
Chondroid differentiation is a common feature of chondroblastoma.<ref name="De" /><ref name="Kurt" /><ref name="Turcotte" /> A typical [[Histology|histological]] appearance consists of a combination of oval mononuclear and multi-nucleated [[Giant cells|osteoclast-type giant cells]].<ref name="De" /><ref name="Ramappa" /><ref name="Kurt" /> However this is not a prerequisite for diagnosis, as cells with [[Epithelioid cell|epithelioid]] characteristics have been observed in lesions of the [[skull]] and [[Facial skeleton|facial bones]].<ref name="Kurt" /> A "chicken-wire" appearance is characteristic of chondroblastoma cells and is the result of [[dystrophic calcification]] that may surround individual cells.<ref name="De" /><ref name="Damron" /> Although, calcification may not be present and is not a prerequisite for diagnosis.<ref name="De" /><ref name="Ramappa" /><ref name="Kurt" /> [[Mitosis|Mitotic]] figures can be observed in chondroblastoma tissue but are not considered atypical in nature, and therefore, should not be viewed as a sign of a more serious [[pathology]].<ref name="De" /><ref name="Kurt" /> There is no correlation between mitotic activity and location of the lesion.<ref name="Kurt" /> Furthermore, the presence of atypical cells is rare and is not associated with [[Cancer|malignant]] chondroblastoma.<ref name="De" /><ref name="Turcotte" /> There are no discernible histological differences observed when comparing the aggressive form of chondroblastoma that can cause recurrence or [[Metastasis|metastases]] with its less aggressive, benign, counterpart.
=== Differential Diagnosis ===
[[Chondromyxoid fibroma]]s can share characteristics with chondroblastomas with regards to histologic and radiographic findings. However they more commonly originate from the metaphysis, lack calcification and have a different histologic organization pattern.<ref name="Damron" /> Other differential diagnoses for chondroblastoma consist of [[giant cell tumors]], [[bone cyst]]s, [[eosinophilic granuloma]]s, [[Chondrosarcoma|clear cell chondrosarcomas]], and [[enchondroma]]s (this list is not exhaustive).<ref name="De" /><ref name="Damron" />
== Treatment ==
== Treatment ==
Chondroblastoma has not been known to spontaneously heal and the standard treatment is surgical [[curettage]] of the lesion with [[bone grafting]].<ref name="De" /> To prevent recurrence or complications it is important to excise the entire tumor following strict [[Surgical oncology|oncologic criteria]].<ref name="De" /><ref name="Damron" /> However, in skeletally immature patients intraoperative [[fluoroscopy]] may be helpful to avoid destruction of the epiphyseal plate.<ref name="De" /> In patients who are near the end of skeletal growth, complete curettage of the growth plate is an option.<ref name="De" /> In addition to curettage, electric or chemical [[cauterization]] (via [[phenol]]) can be used as well as [[cryotherapy]] and wide or marginal [[Resection margin|resection]].<ref name="De" /><ref name="Damron" /> Depending on the size of the subsequent defect, [[Autotransplantation|autograft]] or [[Allotransplantation|allograft]] bone grafts are the preferred filling materials.<ref name="De" /><ref name="Damron" /> Other options include substituting [[Poly(methyl methacrylate)|polymethylmethacrylate]] (PMMA) or fat implantation in place of the bone graft.<ref name="De" /><ref name="Ramappa" /><ref name="Damron" /> The work of Ramappa ''et al'' suggests that packing with PMMA may be a more optimal choice because the [[Polymerization|heat of polymerization]] of the cement is thought to kill any remaining lesion.<ref name="De" /><ref name="Ramappa" />
The primary treatment for chondroblastoma is [[surgical curettage]] and [[bone grafting]]. In some cases, [[en bloc resection]] may be necessary, especially if the tumor is recurrent or aggressive. [[Radiofrequency ablation]] is an alternative treatment option for small, accessible lesions. Post-surgical follow-up is crucial to monitor for [[recurrence]], which occurs in approximately 10-20% of cases.
Both [[Radiation therapy|radiotherapy]] and [[chemotherapy]] are not commonly used.<ref name="De" /><ref name="Damron" /> Radiotherapy has been implemented in chondroblastoma cases that are at increased risk of being more aggressive and are suspected of [[malignant transformation]].<ref name="De" /><ref name="Damron" /> Furthermore, [[radiofrequency ablation]] has been used, but is typically most successful for small chondroblastoma lesions (approximately 1.5 cm).<ref name="De" /> Treatment with radiofrequency ablation is highly dependent on size and location due to the increased risk of larger, weight-bearing lesions being at an increased risk for [[Articular bone|articular collapse]] and recurrence.<ref name="De" /><ref name="Damron" />
Overall, the success and method of treatment is highly dependent upon the location and size of the chondroblastoma.<ref name="De" /><ref name="Kurt" /><ref name="Damron" />
== Prognosis ==
== Prognosis ==
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.<ref name="De" /><ref name="Ramappa" /><ref name="Damron" /> The rate of recurrence is highly variable, ranging between 5% and 40%, as study results are generally inconclusive.<ref name="De" /> However, local recurrence for long bone lesions is around 10%, with chondroblastoma in flat bones having higher recurrence and more complications.<ref name="De" /><ref name="Damron" /> Recurrences are more common in cases involving an open epiphyseal plate where they can be attributed to inadequate curettage to avoid damage.<ref name="De" /><ref name="Damron" /> Lesions of the proximal femur are particularly problematic because of difficulties accessing the [[femoral head]] for complete [[Excisional biopsy|excision]].<ref name="De" /> Chondroblastoma may recur in the soft tissue surrounding the initial lesion, especially in the case of incomplete curettage.<ref name="De" /> 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.<ref name="De" /><ref name="Damron" /> No histological differences have been seen between recurrent and non-recurrent chondroblastomas.<ref name="De" /><ref name="Kurt" /><ref name="Turcotte" />
Chondroblastoma is a benign tumor with a good prognosis following appropriate treatment. However, due to its potential for recurrence, long-term follow-up is recommended. Malignant transformation is extremely rare.
== See also ==
Rarely, more aggressive chondroblastomas can [[Metastasis|metastasize]].<ref name="De" /> The most common location for metastases is the [[lung]], with some cases also involving secondary bone sites, soft tissue, skin, or the [[liver]].<ref name="De" /><ref name="Damron" /> The prevalence of metastatic chondroblastoma, however, is quite low and is believed to be less than 1%.<ref name="De" /> There is no relationship established between metastasis and previous surgery, non-surgical treatment, anatomical location, or patient age.<ref name="De" /> 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.<ref name="De" /> Prognosis is bleak for patients with malignant chondroblastomas that are resistant to surgery, radiation, and chemotherapy.<ref name="Damron" /> However, patients with resectable metastases have survived for several years following diagnosis.<ref name="De" />
* [[Bone tumor]]
* [[Cartilage]]
While recurrence is the most common complication of chondroblastoma other issues include [[Infection|post-surgery infection]], [[degenerative joint disease]], pathological fractures, failure of bone grafts, pre-mature [[epiphyseal closure]], functional impairment, and malignant transformation.<ref name="De" /><ref name="Damron" /> Complications are less common in patients presenting with chondroblastoma in accessible areas.<ref name="De" /> Overall, patients with more classical chondroblastoma (appearing in long bones, typical presentation) have better prognoses than patients with atypical chondroblastoma (flat bones, skull, etc.).<ref name="De" /><ref name="Ramappa" /><ref name="Kurt" /><ref name="Damron" /><ref name="Turcotte" />
* [[Epiphysis]]
* [[Benign tumor]]
== History ==
{{Bone neoplasms}}
Chondroblastoma was first described in 1927 as a cartilage-containing giant cell tumor by Kolodny but later characterized by Codman in 1931.<ref name="De" /><ref name="Kurt" /> Codman believed chondroblastoma to be an "epiphyseal chondromatous giant cell tumor" in the proximal [[humerus]].<ref name="De" /><ref name="Ramappa" /> This view was changed later by a comprehensive review completed by Jaffe and Lichtenstein in 1942 of similar tumors in other locations than the proximal humerus.<ref name="De" /><ref name="Kurt" /> They re-defined the tumor as a benign chondroblastoma of the bone that is separate from giant cell tumors.<ref name="De" /><ref name="Damron" /> However, chondroblastoma of the proximal humerus is still sometimes referred to as Codman’s Tumor.<ref name="De" /><ref name="Ramappa" /><ref name="Kurt" />
[[Category:Bone neoplasms]]
==References==
<references>
<ref name="De">De Mattos, Camilia B. R., et al. "Chondroblastoma and Chondromyxoid Fibroma." Journal of the American Academy of Orthopaedic Surgeons 21.4 (2013): 225-233. Web. 5 Dec. 2015.</ref>
<ref name="Romeo">Romeo, S., et al. "Expression of cartilage growth plate signalling molecules in Chondroblastoma." Journal of Pathology 202 (2004): 113-120. Web. 6 Dec. 2015.</ref>
<ref name="Ramappa">Ramappa, Arun J., et al. "Chondroblastoma of Bone." The Journal of Bone and Joint Surgery 82A.8 (2000): 1140-1145. Web. 6 Dec. 2015.</ref>
<ref name="Kurt">Kurt, Ann-Marie, et al. "Chondroblastoma of Bone." Human Pathology 20.10 (1989): 965-976. Web. 5 Dec. 2015.</ref>
Micrograph of a chondroblastoma, showing characteristic features.
Chondroblastoma is a rare benign tumor that originates from the cartilage-producing cells known as chondroblasts. It typically occurs in the epiphysis of long bones, most commonly affecting the femur, tibia, and humerus. Chondroblastoma is most frequently diagnosed in adolescents and young adults, with a higher prevalence in males.
Chondroblastoma arises from the chondroblasts in the epiphyseal plate of bones. These tumors are characterized by the production of immature cartilage and are composed of chondroblasts, multinucleated giant cells, and a chondroid matrix. The histology of chondroblastoma shows a distinctive "chicken-wire" calcification pattern.
The diagnosis of chondroblastoma is primarily based on imaging studies and biopsy. X-rays typically show a well-defined, lytic lesion in the epiphysis of the affected bone. Magnetic resonance imaging (MRI) and computed tomography (CT) scans can provide further details about the extent of the tumor and its relationship with surrounding structures. A biopsy is essential to confirm the diagnosis and differentiate it from other bone lesions.
The primary treatment for chondroblastoma is surgical curettage and bone grafting. In some cases, en bloc resection may be necessary, especially if the tumor is recurrent or aggressive. Radiofrequency ablation is an alternative treatment option for small, accessible lesions. Post-surgical follow-up is crucial to monitor for recurrence, which occurs in approximately 10-20% of cases.
Chondroblastoma is a benign tumor with a good prognosis following appropriate treatment. However, due to its potential for recurrence, long-term follow-up is recommended. Malignant transformation is extremely rare.
