Radiological Differences in Chondroblastoma of Tubular and Non-Tubular Bones
Sujata Patnaik, Jyotsnarani Yarlagadda, K Shashank Reddy, Shantiveer Uppin, Rammurti Susarla
1. Additional Professor, Department of Radiology, Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India. 2. Professor, Department of Radiology, Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India. 3. DNB Student, Department of Radiology, Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India. 4. Professor, Department of Pathology, Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India. 5. Professor, Department of Radiology, Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India.
Correspondence Address :
Dr. Sujata Patnaik,
404, Sai Kausalya Apt 1-2-384/1,
Gaganmahal Main Road,
Telangana, Hyderabad-500029, India.
: Chondroblastomas are rare bone tumours accounting for only 1% all primary bone tumours. Epiphysis of long bones are most commonly affected, where as the flat bones, short tubular bones and apophysis of long bones are comparatively less commonly affected.
Aim: This study is aimed at finding out radiological differences when the tumour arises in tubular and non-tubular bones.
Materials and Methods: This retrospective study was conducted in the Department of Radiology, Nizam’s Institute of Medical Sciences, Hyderabad, India. All histologically confirmed cases of chondroblastoma were analysed with respect to their imaging findings.
Results: Of the total 22 cases (including 13 females) that could be included in our study over seven years, 17 had lesions in long bones. Youngest was eight years old and the oldest was 40-year-old female. Four cases were associated with Anuerysmal Bone Cyst (ABC) and one case was associated with Giant Cell Tumour (GCT). Femur was the most common site (n=7) followed by tibia (n=7) and humerus (n=3). There were one each of calcaneum, talus, mandible, maxilla and iliac bone involvement. Epiphyseal lesions were seen 10 out of 17 tubular bones. Epiphyseal lesion extending to metaphysis were observed in seven. Typical site, geographic lucent lesion, matrix calcification and sclerotic rim were observed in 10 cases of long tubular bone and diagnosis was straight forward. Sclerotic rim, matrix calcification, periosteal reaction, coarse trabeculations and pathological fractures are common in lesions of long tubular bones. Soft tissue component is common in flat bone lesions. Tarsal bone lesions are most often associated with GCT/ABC and joint effusions.
Conclusion: Chondroblastoma is more common in tubular bone and mostly around knee. About half of them show characteristic imaging features. Flat bone lesions are rare, show soft tissue component and appear aggressive. Tarsal bone lesions are mostly associated with GCT/ABC and joint effusion. Lack of calcification in non-tubular bones is characteristic and adds to the difficulty in diagnosing the tumour.
|Keywords : Aneurysmal bone cyst, Chondrosarcoma, Giant-cell tumour|
Chondroblastoma (otherwise known as cartilage containing giant cell tumour or Codman’s tumour) was first described as a variant of giant cell tumour by Kolodney in 1927; and a year later it was named as calcifying giant cell tumour by Ewings (1). In 1931 Codman termed these tumours as chondroblastic giant cell tumours and finally the term ‘Benign Chondroblastoma’ was introduced in 1942 (1). Chondroblastoma accounts for 1% of primary bone neoplasms occurring 2nd decade with age ranging from 8 to 50 years. Males are more affected than females with a ratio of 2:1 (2). Pathologically they are derived from primitive cartilage cells. Polyhydral chondroblasts, multinucleated giant cells along with nodules of pink amorphous material and chicken wire calcification (pericellular deposition of calcium) is virtually diagnostic on histology. Long bones are the most common site. Epiphysis of proximal Keywords: Aneurysmal bone cyst, Chondrosarcoma, Giant-cell tumour femur, distal femur, proximal tibia, and proximal humerus are common sites. Apophysis of long bones, flat bone, short tubular bones of hand and feet are less common sites (3). The objective of the study was to report the distinctive imaging characteristic lesions of non-long tubular bones as compared to changes in typical long tubular bones.
|MATERIAL AND METHODS|
This study was conducted in the Department of Radiology, Nizam’s Institute of Medical Sciences, Hyderabad, India. It was a retrospective cross sectional analysis of 22 consecutive histopathologically proven patients of chondroblastomas over last seven years (2009 to 2016). Radiographs and all cross sectional images (either CT or MRI) were analysed. Various radiological features in terms of site, size, border, sclerosis, calcification, trabeculation, cortical disruption, periosteal reaction, soft tissue component, oedema both soft tissue and marrow were studied. Association of other pathologies like ABC, GCT were also noted. The cases operated or treated earlier were not included in the study. The cases with nondiagnostic histopathology were excluded from the analysis. Critical analysis was made to observe any difference in imaging characteristics of long tubular bone lesions from lesions in other sites. The design, conduct and write-up of the study were notified to the Institutional Ethical Committee.
Study patients were 22 which included 13 females and 9 males. Youngest was eight years old and the oldest was 40- years-old female. Four cases were associated with ABC and one case was associated with GCT. Femur was the most common site (n=7) and tibia (n=7) and humerus (n=3). There were one each of calcaneum, talus, mandible, maxilla and iliac bone involvement. Involvement around knee was seen in 50% (n=11) and upper end of tibia was the most common site (n=7). Epiphyseal lesions were seen 10 out of 17 tubular bones (In 2 cases apophysis was the site of involvement). Epiphyseal lesion extending to metaphysis were observed in seven. Typical site, geographic lucent lesion, matrix calcification and sclerotic rim were observed in 10 cases of long tubular bone and diagnosis was straight forward. Imaging findings of all cases are tabulated in (Table/Fig 1).
Sclerotic rim, matrix calcification, periosteal reaction, pathological fractures are common in lesions of long tubular bones. Calcification is less common in non- tubular bones. Sclerotic rim and joint effusion are observed in tarsal bones and soft tissue component in flat bone lesions. Another significant finding was coarse trabulations in tubular bones and thin trabeculation in tarsal bones. Diagnostic dilemmas were encountered in six cases of tubular long bones and in all cases of non- tubular long bones, as depicted in (Table/Fig 2),(Table/Fig 3),(Table/Fig 4),(Table/Fig 5),(Table/Fig 6),(Table/Fig 7),(Table/Fig 8),(Table/Fig 9),(Table/Fig 10),(Table/Fig 11),(Table/Fig 12),(Table/Fig 13).
The radiological diagnosis mentioned below was representing the diagnosis made before any operative/biopsy procedure.
Though the lesions were in typical site in long tubular bone, because of ill-defined border, lack of calcification confused with GCT (n=4), large soft tissue component with calcification and cortical disruption are thought of chondrosarcoma.
Retrospective analysis of 22 cases of chondroblastomas showed varied radiological features. Age ranged from 8 to 40 years with male predominance (13:9) in the present study similar to most of other studies. In a study of 31 cases by Jaovisidha S et al., concluded that an increase in age by one year reduced the risk of having tubular bone involvement by about 27% when compared with NTBs (4).
The most common site is epiphysis of long bones (70%), distal and proximal femur, proximal tibia and proximal humerus (Table/Fig 14).
Para acetabular area of innominate bone, ribs, skull, mandible, maxilla, vertebra, scapula, patella, and sternum are rare sites. Unusual but classic sites are talus, calcaneus and patella (Table/Fig 9),(Table/Fig 11) (3). In craniofacial region temporal bone is commonly affected (5). In our study involvement around knee was seen in 52% (n=11) and upper end of tibia was most common site as described in many studies. NTB sites were three in flat and two in tarsal bones. Posterior aspect of calcaneum at talocalcaneal articulation is the most common site of calcaneal involvement as observed by us. It is speculated that tumours at talo-calcaneal articulation may be from cartilage rest from articular cartilage. Typically, chondroblastoma is a slow growing tumour in epiphysis and is eccentric expansile round or oval or geographic lucent lesion with complete/partial, focal sclerotic rim (Table/Fig 15) (6).
About 80% of tumour are 1-4 cm but may be as big as 8 cm. When small lesion is mostly confined to epiphysis and when large it extends to metaphysis (Table/Fig 16).
Lesion is homogenously lucent in 40% and in 60% there may be mottled appearance. Opacities are due to septae and calcification are best seen in CT. Calcifications are ring or arc like. Close differentials are GCT, ABC, and histiocytosis. Because of lack of sclerotic rim, lack of calcification four of tubular the bone lesions, both the lesions in tarsal bones and one iliac bone lesion were misdiagnosed as GCT. When large, the lesion can cause scalloping, cortical break and periosteal reaction. Epiphysis is intra articular and has no periosteum. Hence, periosteal reaction is seen along the diaphysis in about 50% of cases in literature. Periosteal reaction was observed in 5/17 (29.4%) of our cases (Table/Fig 7).
CT depicts the matrix mineralisation, soft tissue extension, cortex erosion and fluid-fluid level (Table/Fig 10).
Calcification is noted in 20-50% of cases (Table/Fig 3),(Table/Fig 8),(Table/Fig 12) (7). The fluid- fluid level is due to association of secondary ABC which may be in 15% cases (8). On contrast administration there is mild enhancement. Four out of 22 of our series were associated with secondary ABC and one had GCT. All the four cases (two in tarsal and two in long tubular bones) there was fluid-fluid level.
The characteristic signal intensity of chondroblastoma in MRI reflects cellular stroma which is low signal on T1W images and high or variable signal on T2W images (Table/Fig 17) (8). T2W hypointensity represent abundant immature chondroid matrix, chondroblastic hyper cellularity, and hemosiderin. Lesion may contain fluid-fluid level and sometime lesion may be solid and show heterogeneous enhancement. There may be cystic component in the lesion. Periosteal reaction and marrow oedema are other features observed in MRI. Joint effusion is a feature in 30-50% cases, which we observed in 9/22(41%) cases (Table/Fig 10),(Table/Fig 11). Both the cases of tarsal bone lesion and one case of iliac bone lesion had joint effusion.Tumor may penetrate the cortex and extend to adjacent soft tissue in small percentage of cases and some literature says it can occur in 10% (9),(10). Four cases had soft tissue component with calcification, were mis-diagnosed as chondrosarcoma; but HPE proven to be chondroblastoma. One was mandibular condyle lesion, two in distal femur and one Iliac bone lesion were confused aggressive GCT.
Flat bone involvement is seen in older age group and is rare. Mandibular condyle is still rarer (8). Usually these lesions are aggressive in appearance (11). The only case of mandibular condyle (40F) had aggressive findings like expansion of bone, cortical disruption, enhancing soft tissue component, and calcific foci. Chondrosarcoma was working diagnosis and histopathology confirmed to be chondroblastoma (Table/Fig 4).
Although, chondroblastoma are benign, large size, joint effusion, soft tissue invasion, local recurrence, pulmonary metastases indicate aggressive nature. Flat bone lesions are more aggressive than the long bone lesions (12). Due to hyperaemia, lesion may show avid uptake. Often it shows increased FDG uptake though it is a benign process (14). Angiography is done as preoperative road map.
Prognosis of chondroblastoma is good. About 80-90% cases are successfully treated with curettage and graft. Radiofrequency ablation is other treatment option. Recurrence occurs in 14-18% within two years. All our cases were operated.Incidence of aggressive chondroblastoma is low and is <1%. According to Huvos and Marcove recurrence of chondroblastoma is 24% in three years and 100% when it is associated with ABC (14). Signs of healing are cessation of symptoms, marked sclerosis surrounding lesion, centripetal calcification or ossification, obliteration of bone grafted or curetted or grafted area. Recurrence of lesion is suspected when there is increasing lucency with reappearance of symptoms. Recurrence is more common when chondroblastoma is associated with ABC. Metastasis is uncommon. It is common when there is recurrence and it metastasises to lung. Soft tissue/skin, bone and liver are other sites of metastases (14). Lung metastasis may be nonprogressive and can be treated with surgical resection or may be followed up conservatively.
This is a retrospective analysis with only a limited number of cases included. Hence, the conclusions are only suggestive. Larger studies are recommended.
Chondroblastoma is more common in tubular bone and mostly around knee. About half of them are showing characteristics imaging features. Flat bone lesions are rare and show soft tissue component and appear aggressive. Tarsal bone lesions are mostly associated with GCT/ABC and joint effusion. Lack of calcification in non-tubular bones is characteristic and adds to the difficulty in diagnosing the tumour.
|TABLES AND FIGURES|
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